I hate to burst your bubble, but, posting an active eBay link isn't allowed. But, there might be other sites in the European Union region itself that might have that.

That reminds me: I'm planning on purchasing this in case the PSU in my Packard Bell goes kaput and one for my Socket 7 machine since that has the P8/P9 connections on there and the old rocker switch I still have.

Don't worry its already burst trying to find a ATX to AT adapter (since I can not find a AT PSU (or an AT case for that matter)) that appears to be safe and won't cost too much. Anyway,m thanks for pointing that out. Still trying to orientate myself here.

I recently found out that some older ATX PSUs (I'd say pre-2005) have a -5V rail. The 20-pin connector will have a white wire if that's the case.
All you need at that point is the cheapest ATX to AT adapter from eBay as it also includes the white wire (I bought one for a Socket 7 motherboard recently, works perfectly).
Of course, this is assuming you have such a PSU, but it shouldn't be a problem sourcing one locally (it's mostly the cheap old no-name brands no one wants).

Humm, certainly something to consider. Need to be carefully the PSU won't go pop soon though...

AT switches it actually off through the motherboard while ATX is a soft off that retains standby power.
There is an actual power switch on the back of many ATX power supplies, but it would still require some soldering on 115/230V rails to get that somehow to switch of ith the system.

For AT PSUs the issue is finding old units that still work without issues. For older ATX systems one can just buy modern units, decently sized if the 5V rail hs to be strong.