If you don't want to customize the KOP Joysticks, you can always try to "build your own" joysticks.
Happ Controls sells tons of old coin-op video arcade replacement parts such as buttons,
analog joysticks, trackballs, steering wheels, speed shifters, and more.
I like to browse through there whenever I am looking for cool ideas for our operator interface. Last year, our team bought a whole bunch of the push buttons from them for
our operator interface from last year.