I have a ksc usp compact it seems that the rear sight has chipped at the bottom. After disassemble to my disappointment i found out that there is a long screw that holds the gas blowback block to the rear sight (pretty bad design if you ask me.) So in conclusion unless you can some how create threads in the bottom of the trijjicon rear sight it would not be possible to replace them.
"A hero is no braver than an ordinary man, but he is brave five minutes longer"
-Ralph Waldo Emerson