GeekForce

When game geeks get stuck:

http://www.multigame.com/pacplus.html

Clay is legendary in the game-geek community. He’s created several “multi”
kits that allow owners of vintage arcade machines to play several titles
on their machine by attaching daughter-boards to their cpu’s. He used to
make multi-pac man kits, but his williams multi-kits are the rage now. The
units are often found in reconditioned williams cabinets with new vinyl,
glass and side graphics, and retail for a couple of grand:

http://www.phoenixarcade.com/art.htm#multiwilliams

The best part is that it requires the owner to have the actual game to
enjoy his fruits, which not only prevents piracy, but helps keep antique
hardware alive.

Monty