Unfortunately, it is way too wide. If I could just imagine one and pop it into existence it would be about 6cm wide.
Due to the low amount of keyboards I found that are extremely small, I would be fine with one being maybe 10cm wide. But that should be the absolute max. Else it does not work for the purpose I want to use it for, in the first place.
What I don’t really understand is, that there are so many Blackberrys and similar phones, that have an attached irremovable keyboard that is always super tiny. However finding an unattached keyboard you can attach somewhere yourself of this size, is like trying to find a needle in the hay stack. So far I only found 2 keyboards that are at least close to the size I need, but both aren’t really good and it wouldn’t be so great if I really had to resort to them.