I guess all u need is buy it from the neo-store at :
http://www.neostore.com/detail.asp?ProductID=663
If the mvs have a socket-bios type, all you need is to swap them.
Otherwise (like in the aes case) you have to de-solder the old chip, or mount the new over the old and cut some contact.
To me seems you asked about a 40pin eeprom, the ones needed to re-dump the internet roms in a "sacrifical" cartdrige.
This mean convert a cart, without a mvs one.
anyway, I guess if this is possible (of course yes).
So .. what do u wanna do today?