I make mine out of buffalo horn, it's really inexpensive. Picked up a piece made for scales on custom knives at Blade last year for less than $6.00. Cut out the basic size with a hacksaw, higher count teeth. A metal or wood pin is fit to the bottom of the saya. Create two holes in the kojiri, one to mate to the pin, and one to fill with epoxy...not real picky with brand...Devcon two ton is good.
Before doing any glue up, finish sizing the horn piece. Mix up glue and clamp in place. If already on a laquered saya, I use 1 wrap of 3M painters tape to mask the laquer,, and glue it up. I put a hole in the horn and a hole in the bottom of the saya wood to act as a liquid pin that soldifies and then I sand by hand up to about 1500 grit.
Power tools work well, but it can be done by hand with patience.
Best Regards,
STeven Garsson
