There are a number of 24 to 28 pin adaptor boards on eBay as Ye Old Commodore 64 computers have the same issue. I used some in my 468 some time back with the usual Mostek Rom failures. Some of these a

I believe the ROM images are on Tekwiki, I think that is where I got them when I needed them. You will most likely have trouble finding an original 24 pin Eprom, but I used (as i understand most do) m

Hi Michael When you go into the thingiverse article the front panel is there also, but needs cut out for the pull tab etc to be added. Steve.

There is an unfinshed one on thingiverse as part of an upload under "Tektronix TM500 module parts" that someone has uploaded, it may be a good starting point?