I have a couple of the Memotech keyboards, and for the time they were excellent [1]. I picked up one of David’s ZX key keyboards a couple of years ago and it’s also great. He has a fun read about the adventure of building this keyboard [2].

[1] https://www.timexsinclair.com/product/memotech-keyboard/ [2] https://www.zx81keyboardadventure.com/2019/02/zx-key-externa...