I offer $100USD + shipping, for the A4000 without any of the extra expansions. Basically I need the system itself, with the CPU card and 2MB chip ram, and nothing else. I'd offer more, but it looks like it could be a non-working system as you can't confirm whether it's really only the power supply that's failed. No pictures, no information about the battery (e.g. leakage/corrosion), no info on the buster chip revision, no info on whether the SIMM slots are broken or not...$100 should be OK, I believe.
Let me know by PM if interested.