I recall seeing an Eastern Block manufactured ZX81 clone with a mechanical keyboard back in the day, and a couple of different Soviet era ZX81s with not-mechanical-but-vastly-improved keyboards. Seems like they really liked to clone the ZX81 behind the Iron Curtain.

That said, really isn't new. Lots of people took ZX's and modded them with new keyboards, bigger cases (better thermals & PS), better mechanical connection for expansion ports, etc.