ATX is ATX. Any modern case should work with any old ATX motherboard.

As far as cases for AT motherboards, you won't find anything new. Best you are going to do is an ATX case that has mounting holes that line up and then you can either make or buy an AT I/O shield.

i must have a really cheap micro atx case then. None of the holes line up with my micro atx ali k-6-2 board.

Maybe if i opt to buy a bigger case they will line up , i.e. regular ATX mid tower. some of these mobos have like 7 ISA /PCI slots and would probably need a regular tower

This is one reason I really like industrial rackmount cases... Every possible mounting hole possible.

Anyway, when shopping for cases, it is usually pretty easy to see what holes they have to mount the motherboard if they have half-decent pictures.

Are you located in the USA? If so, I might have a case you could have for the price of shipping. I really only have a single micro-atx motherboard that I might actually use and have 2 or 3 micro-atx cases.

Pics of the motherboard you have would be great so I could check if one of the cases I have would work.

If a standard micro-ATX mainboard doesn't fit it can't be a standard case or mainboard.

Many holes is the same on baby-AT and ATX so its sometimes possible to put an AT board in an ATX case.

If you have a full ATX case you should be able to fit a Baby AT motherboard in it with two complications:

1. You'll either need to do without an I/O shield, try and find a premade one, drill a hole for the keyboard port in a blank one, or 3D print one
2. Because AT cases had 8 slots, and ATX has 7, you'll lose one slot. Usually this is a non-issue. Later 486 boards with onboard IDE often don't have the 8th slot anyway.

Even if you can cram a Baby AT motherboard in a MicroATX case, you only have 4 slots. On a 386, once you have video card, I/O card (usually needs a second slot for the other serial port), sound card, and Ethernet card, you're out of room.