I have the file(s), it looks like the link is still up and working, scroll down a bit and get the "Carts and system" one: https://forums.bannister.org/ubbthreads.php?ubb=showflat&Main=7371&Number=84191

"Microvision header and bottom controller": the cartridges are huge and AFAIK the overlays are stuck in them, you don't slide them in like on some other consoles.
If it's difficult to take apart (eg. glued), you might have to break the cartridges if you want just a scan of the overlays.