I wanted to build two ZX81+38 some time ago, but ended up getting components for three since I thought maybe I'll make some bad mistakes on one. I ended up with three working machines, and two of them now have nice enclosures (with different style keyboards).
If anyone is interested in the leftover PCBs (minimum order of 5 from Pcbway) you can have them for the cost of shipping. I'm in Sweden, so I assume it only makes sense within Europe.
For the assembled Z81+38 I believe the total component cost is around 100 EUR, but I'll consider any offers since it's just sitting here anyway. (Notice it comes without any kind of enclosure or keyboard, but if you ask nicely I could 3D print something and/or connect one of the keyboard PCBs.)
Staffan