The MemX boards, the board layout really needs a double-sided PCB, so it would be tricky to DIY, and at the moment there is no confirmed suitable
replacement for the P3 CPU, so it could also be risky - get it right first
time, or potentially render your P3 unusable.
However, when I have spare board space left on a proto-PCB, I can easily
drop in a couple of MemX boards, so I will have some more at some point.
If you want I can put your name on a list to contact when they become
available ?