CZUB's website shows a
CZ 100 with a fixed rear sight. Additionally, I seem to recall someone mentioning in this forum that CZ-USA actually stocks a fixed rear sight for the CZ 100. It might be worth giving them a call to ascertain if that is indeed true.
I personally
like the adjustable rear sight on the CZ 100. The sight's extremely low profile doesn't seem to impair the gun's CCW capability, and actually adds to the CZ 100's overall feature set to make it a great value for the money. Offhand, I can't think of another sub-$350 semi-auto that offers compensator ports, an adjustable rear sight, an eminently tactile and visible loaded chamber indicator, a barrel stop/one-handed racking thingie and a trigger pull that builds finger muscles.
Edited to add: Just noticed that all of the pictures of the CZ 100 in the user manual show a fixed rear sight, and that the dovetail
appears to be the same size as that for the adjustable sight.