I make buki for classical Japanese martial arts -- those whose origins precede the Meiji period. Sometimes I have small generic pieces available, like tanto and tessen, suitable for use in gendai arts like judo or aikido, but my focus is on the specialized morphology required by various koryu arts.
I use several types of wood, but primarily a type commonly called jatoba, or Brazilian cherry. It's not a cherry at all, but it does have an attractive reddish-brown color with small bird's eyes in the grain, and it does stand up to some pretty hard use. I've also used woods like Purpleheart, Black locust, and Osage orange, but those can be difficult or nearly impossible to find in lengths suitable for weapons of bokuto size or larger.
As of the summer of 2017 I've finally finished my Bachelor's degree and am working at getting back to making buki. I still have to cope with the fact that it's my full time job that pays the bills, though, and I have my own training to look after.
If you need buki and you're training in a koryu under a qualified instructor, send me an email and I'll see if I can help you out: queries at bethsbuki dot com.