Unfortunately, there are no other keyboards for the Ubook X.
However, other manufacturers use the same dock connector (there is a USB 2.0 + a totem pin).
I helped myself to Wortmann. Although these have slightly different dimensions, the DOCK connection has the same dimensions. To be precise, only 1-2 mm larger. Only the magnets are installed with polarity reversed by exactly 180 degrees. But that’s easy to fix.
TERRA TYPE COVER PAD 1262 [UK] | WORTMANN AG - IT Made in Germany
I had already written something here, including how to turn the magnets. I am still very satisfied with the keyboard today.