The studio I worked at during that time actually did have a CPU slot based memory extension that can handle I believe up to 256 Mb, this would have been around 92 or 93, but I'm not sure how early it was offered on the market that's just when I started there and it was already in the shop.

I don't recall the name of it though but I remember that it was a peculiar PCB design, with part of it resembling a breadboard. I think the name started with Ex, like Excelsior or Excalibur or something like that.