The ZX80 is another old computer that can be made very close to the original ( there are no special chips inside, and most of them are still being manufactured. The DIP version of the Z80 CPU is famously no longer being manufactured since last year and the RAM chips probably aren't either, but there's no shortage of new old stock for both).

If you want to make your own: http://searle.x10host.com/zx80/zx80.html

My build log (including Gerbers based on Searle's foils): https://blog.qiqitori.com/2024/03/building-a-new-zx80/