certain coolers have a metal clasp that's long enough that you can bend it to fit socket 4. i've done this once with a s7/s370 cooler that's sold under manhattan, startech and maybe other labels. worked fine, but i've only used it for a short time and i don't know if there might be some mounting pressure issues on the socket long-term, because the cooler is a lot taller than any actual socket 4 cooler. the other caveat is that of course you need the correct mounting tabs on the socket, but the common batman's revenge board does have this.

My only Soc 4 cpu has a 50mm x 50mm aluminum HS glued to the P-60 cpu. (is an OEM cpu+hs p/n 616971-001 <IBM or Compaq>)
Any 50mm x 50 mm x 20mm would work with a proper clip or adhesive pad...

I used 3M thermal adhesive tape to attach the heatsink to my P60, works great. Looks like it was originally stuck on with some sort of thermal epoxy as some traces and marks remain on the CPU, but when I got it they were already separated.

Also, the Socket 4 on my Batman's Revenge board has no tabs at all (and it's not that it had tabs that were broken, it just doesn't have any), so gluing the heatsink to the CPU seems like the only option in my case. There are a couple of holes near the socket which I suspect may have been used for a custom fan/cooler assembly, but not sure about that.

Measurements are as follows: base 55x50mm, height 21mm

You can use a much smaller heatsink because you always want to have a fan blowing air on it. Even a large heatsink like mine gets really hot really fast without any active cooling. I think most cases back then had the bare heatsink with some fan nearby providing some airflow, but nowadays a fan on top of it seems like the simpler solution.

As a collector, gluing to the cpu is not feasible.

I already used a metal bracket (the asymmetrical hooks) and it almost fried the cpu as it came off.
It was a big scare 😀

Probably I'm stuck on a DIY solution