There were some Microsoft wireless+optical mice that were dual USB and PS/2, with a passive adapter to convert the USB plug to PS/2. No idea if they worked well with KVMs.

e.g. http://www.telecommander.com/pics/links/mice/ … relessoptrt.htm

I can confirm that all the older Logitech wireless bases were "combo".
The really old ones were PS2 and serial, definitely not including any optical ones.

But USB-PS2 combo via the passive adapter, there should be some around.
Probably not with the "unified" fingertip-sized ones, but those that still had a cable.

The KVM - rather up to chance. The "real" ones shouldn't care what you attach but...

There was a Microsoft Wireless Optical Desktop Pro set I had for a while, had PS/2 and optical mouse... reason I stopped using it though is because it shorted or something and PC acted dead until I unplugged it, thought the damn thing had killed my PC but all seemed fine... big lump of a receiver though and not much range... and for all the ad copy crowing about battery life it ate a set about every month.

I bought some passive PS/2 adapters but I guess those don't work with those tiny nano adapters, which is why I've started going down this rabbit hole.

I've found several wireless mice that have base stations that seemingly work with these converters so I guess I can try one of those. Hopefully they handle well (early 2000s wireless mice were...eh as far as tracking goes, I guess due to low polling rates between the unit and the base station, but I know what tree I'm barking up).

There definitely are quite a few around like this:
https://www.ebay.com/itm/265605668109
https://www.shpock.com/de-de/i/X1z6F9mtCyv9en … t-optical-mouse

But those are roughly 20 years old. So it remains a question whether they still pass as a comfortable mouse today.
I remember that second general pattern to use two AA batteries which made them rather heavy. AA to AAA converters can help.

I found a chart once that showed which logitech cordless device will work with which base, but failed to bookmark it.
But as I remember - boy, what a mess. How many different ways can there be to transmit a mouse signal over one meter?!?

So, you said it. Rabbit hole. 😁

To be fair, whatever mouse I settle on is going to be used with a period-accurate machine hooked up to a period-accurate display so I don't need massive DPIs to get around the display, just something that would have been relatively comfortable enough at the time. I'm not looking to use this on a 1440p desktop or the like.

I just don't want to have a wired mouse. I just can't stand the thought of using one anymore with how annoying it is to work the cable around your desk.

My brother used to have the MouseMan optical, first link.
Think it was rather advanced for the time.
You need to be right handed for that one. But if you live in the USA, for $16,47, I'd give it a try.

The receiver is in the last photo there. It's the "half ellipse shape" type.

Might be the last model before this one:
https://www.ebay.de/itm/Logitech-m-n-ps-2C-BT … r-/223801689139
So, that still came with a PS cable - at least some of them. And should support slightly more modern mice.
Afaik, after that type came the nano USB ones.

Update time: I went on eBay and decided to take a stab at this:

Shipping was a bit steep but the seller did accept my best offer so I bought it. Got here today, plugged it into my KVM, and it works (including the still-wrapped 10 year old batteries, no less)! Even in Windows 95 it has no issue seeing the mouse through the KVM.

So now I just need to replace the KVM itself (it requires a little hockey puck remote thingy to swap back and forth and when I bought it I didn't know that so I didn't have it at the time -- I might go back to the computer shop where I got it from to see if they have the little puck but I doubt it) and get some hookups so the audio for each PC will go to the speakers without needing my intervention (the audio passing through the KVM is noisy, IMO, so I'm going to get a female-to-2x-male 3.5mm splitter and two short 3.5mm extensions to run between the two PCs directly -- I already do this with a pair of PCs in my other residence and that seems to work without issue so long as both systems aren't outputting audio at the same time).

Then I can finally start using these retro PCs.

Congrats, that looks like a rather recent model. Might even be an early laser type?

So, that's the usual way to determine it does PS2: The adapter is included. No point hoping for correct documentation from either the manufacturer or the retailer, just not gonna happen.
But, I still do respect Logitech. They tended to be rather conservative with their support for legacy standards. Just their device-base pairing is a bit of a mess and of course, build quality deteriorated like with anything else.
Quite a testament to Duracell that the AA did not leak. Cheap alkaline cells are perfectly capable of doing that on their very own after a few years. Some D-cells on a shelf did that here, actually making a noise by venting gases.

Is it one or two cells? If two, consider getting AA-AAA converters to reduce the weight. Or some AA Lithium cells. Expensive AF, but much lighter and last forever.

What model is that mouse? You should always include that around here so others may find it, maybe looking for the very same info.

Two AAs.

The listing says it's an LX5.

The DPI on the mouse seems pretty good. More than capable of getting around a 1280x1024 resolution display without running out of runway.

I had a wireless mouse that ran around my garage and made a nest in one of my boxes a few years ago 😁
Glad you found one that has worked .....