Jim Francesangeli of Echo Lake Pinball is making brand new replacements for Game Plan MPU-2 (which works for MPU-1). See this thread:
https://pinside.com/pinball/forum/topic/game-plan-mpu-2-replacements-ready-for-orders
Here is contact info:
Jim Francesangeli
Echo Lake Pinball Service & Sales
925 Marwin Dr.
Hinckley, OH 44233
tel: 330-278-2228
email: [email protected]