I suspect it will score and snap just fine with one of these....
https://www.lowes.com/pd/Cutter-1-in-T-x-4-in-W-x-6-in-L-Silver-Plastic-Sheet/1001463532
They have been around for decades for cutting laminates, polycarbonate sheet etc. Kydex is available in a dizzying aray of colors, patterns...