You would need to pick up an eprom programmer/eraser and some eproms, that would run about $100. Eproms have a slow turn around time, about 20 minuts between programming, so you should consider geting several eproms so you can shortin that cycle. I would look to pick up 10 at least, and they should cost between $2-$6 apiece.
That cart takes 32 pin, 8 bit, 5V eproms in the 4mbit-8mbit range, You can use the following part numbers:
M27C401 – if you can find it
You should try to get eproms in the 80ms range but anything from 80ms-120ms should work. If the eprom is to slow you will have to run the virtual boy off of AC power in order to stabalize everything.
If you can find a flash or eeprom in a 32 pin dip package it would be a better way to go, but eeproms are VERY expensive, and flash usualy comes in a surface mount package.
Yes, that would work great, get the 70ns chips. Most any eprom programmer should be able to handle a 32 pin flash chip, but verify it before you purchase something. Also you should get a pair of ZIF sockets to put on the cartrige. Thease are dip sockets that have a switch so you can remove the flash without bending up the pins. There between $5-$30 depending on where you get them and what style (id go for the low profile ones myself)