I designed a replacement for the original cartridge, specifically the PCB for it.
I found the housing design for printing on a 3D printer on Thingiverse. A bit tight, but it can be assembled.
You can mount 27C128 or 27C256 memory to the socket.
It works

Gerber files attached.

There is no need. I made one more PCB.
I just haven't tested yet.

Great idea! There are a great number of users without a cartridge to try.

And I see that you have added a read-only/write switch, so the content can be modified easily in situ from the Enterprise, for example fitting an AMD 64KB flashRom and with Zozo´s SD cartridge updater app.

Attached are the schemes with the values of the elements.