What about having a set made from Micarta or Carbon Fiber?
If you have an older military styled knife with a screw on butt cap, and a little extra room in the handle, you can make it work.
- Disassemble the knife down to the tang, and thread the knuckle/guard on.
- Butt handle up against the inside of the guard (against the tang) and mark how much handle material has to be removed.
- Remove offending material
- Reinstall your new sized handle and the knuckle/guard bottom support.
- Reinstall the butt cap with some loctite.
I am sure some of the Knifemakers here can make your the knucke/guard. Especially the ones that sell knuckles/"paper weights" on the exchange.