All Sanwa FLAT PLATE JLF levers and compatible plates work perfectly with the Panzer Fight Stick 3. Additionally, the HORI HAYABUSA (Standard and Optical) lever works as well since it shares a common mounting pattern on its plate. Finally, Seimitsu Levers using FLAT PLATES (NOT SS PLATES) should work fine, though their final height might be lower than you want or desire since they are designed to sit flat against the metal panel. I am unable to personally verify each lever compatibility, so please refer to the levers technical specifications and the mounting point specs below.
Here's a handy reference for the Panzer Fight Stick's lever mounting system:
Some folks have modified their plates by dremeling out the mounting holes a bit or by replacing them completely with "universal" plates available from a lot of retailers. Both are great options for the more tech savvy person. My personal recommendation is to use a Sanwa JLF as it's my personal favorite lever.