I think that is what you need. Contact VST, they will let you know for sure.
Might be worth seeing if they have one with OS 1.20, if you need that in particular to work with a card reader.
I guess that you have to open the MPC, plug that ROM into an IC socket inside the MPC, boot from it, fix your OS flash ROM, then remove it. It will come with instructions, or VST will be able to let you know how to do it.
Looks like that is a standard EPROM chip, not a specialised board like what is needed for the MPC2500, which probably makes it easier to get hold of.