You'll actually need yourself a full A and B set for the multi kit - ideally on rev 6/7 so you have the CN9 connector, the Marvel games tend to be good donors because they tend to be cheaper and on the later revision boards
Good luck with your search
@kuze has an X-Men vs SF that should suit fine, the shell is the wrong colour but that can be easily fixed by repainting
I actually have a copy of AVP coming that is the USA B board so I need a blue or green A board to go with it. I do plan to look into the multi down the road though!