Unfortunately, all this time, Kydex sheets are only available by BULK from where I live in. Far too expensive for me.
I've had quite an interesting discovery, though. I've tried out coating a piece of cardboard with a thick layer of hot glue. I shot it a few feet away, (with an Ares T.A.R. 21 Tavor, shooting 350 fps) and the sucker just bounced back at me (I meant the bullet). I also tried making a contact shot at the hot glue. Not much damage either. Both shots made very shallow dents, barely visible that I actually had to look for them. This may be fixed by reheating it, letting the glue set in a partially liquid state, then dry. I haven't tried that, but I'll let you guys know as soon as I do.
One problem with hot glue is that it could only be used inside Halo armor, unless you're okay looking like a snot-covered Spartan.