they don't do it; but I can recommend my luthier. He'll do a bone nut for about $65. you can ship your neck to him.

www.guitarspecialist.com/frontdoor.htm

regards.
Martin HD28-KM
Breedlove SJ-25-12W and SC-10M
Fender US Strat thru Fender Cyber-twin
pix: http://www.angelfire.com/jazz/peterkarl/guitars/index.album?i=0