Raspberry Pi shield
I seem to recall that someone used to sell a Raspberry Pi shield with a P1 chip that plugs into the expansion port on a Raspberry Pi. In fact, I have one. I'd like to buy another though and I'd like one that doesn't have the connector installed. My idea is to use it to replace the Raspberry Pi in a PiDP-8i. The PiDP-8i is itself a Raspberry Pi shield but it seems like I should be able to solder male headers onto a Raspberry Pi shield and use it to replace the Pi.