You need one of this style:
https://www.ebay.com/itm/Turbo-Cool-300-AT-Po … &frcectupt=true

I have full size AT tower that uses a PC Power & Cooling 300W Turbo Cool power supply like that. You might find something cheaper if you search for some of the terms from that listing. I'm not sure if there's a specific name for the size\format of this unit.

To be honest though, unless you really need it to look 100% factory mint and period correct, I'd just modify the case to use a standard ATX power supply and use an adapter. The old power supplies are noisy and inefficient.

You can get one of these:
https://www.ebay.com/itm/SEASONIC-300W-POWER- … &frcectupt=true

And one of these adapters:
https://www.ebay.com/itm/NEW-ATX-to-AT-Mother … &frcectupt=true

And it will work for almost everything. It won't have a -5v rail, but only a few specific older sound cards need them. For a while there was a guy making those adapters with a -5v line added (I bought some) but he doesn't appear to have any at the moment.

I need just AT power supply case, can be without electronic just box, I want to put inside new ATX electronic

n0m4d wrote:

I need just AT power supply case, can be without electronic just box, I want to put inside new ATX electronic

I would check eBay or other places for listings that contain a lot or a group of "for parts" power supplies then. You may find one that way for cheap. Also, check any old computer shops or electronics recyclers in your area. Now that you know what they look like, it is just a matter of looking for one.

There is also the possibility of just replacing the board inside the PSU with one of a new ATX PSU (preferably 80plus Platinum) when the old one in your AT cooked off.
When doing this, it pays off to add some PSU cables, as the original AT PSU cables had very few connectors, and no 3.5" FDC and SATA connectors at all.
Also important is to rewire the fan (bypassing the idiotic thermal regulation), because ATs were constructed with fan running full speed in mind. If you skip this step, your mobo and disks will likely be cooked.
I did this a lot of times back then.

The -5V can be made via a 7905, if any need. But it's better to take a quality PSU that still has --5V imho.

Of course doing all this is only recommended if you are familiar with high voltage electronics and hazards of shock and fire involved if one makes mistakes.