Toshiba VDP 50K

You can read most of the info on the VHD wiki page. You’ll find that 4 different interface cartridge models were produced but finding one will be tough (but patience and a bunch of cash will help).

All VHDpc interfaces should work OK with all VHDpc enabled players. This was the idea behind the VHDpc specification: you could control any VHDpc player from any VHDpc enabled computer/appliance. But, as the VHDpc interfaces are so rare, it's hard to determine how much the implementations are adherent to the original idea.

I updated wikis about VHD. The interface IF-C9C for the HC-90 / HC-95 probably supports the VHDpc standard but I did not find any confirmation.

https://www.msx.org/wiki/VHD

Do you know VHDpc discs?

this is the next question: maybe someone has an interface scheme?