HP2100 boards on Ebay
there is an auction on Ebay "Kleinanzeigen" (classified) in Germany for various HP2100 boards:
and another for the core memory:
I have no 2100 (yet), but may someone needs some spare boards. At least it makes sense to have them in store for later needs. It's always good to salvage those parts from beeing scrapped. If you need assistance in buying / shipping, let me know.