Recently I've been looking to replace my white oak bokuto with saya that I normally use. While white or red oak are both good woods to make bokuto out of they eventually wear down and start to splinter and crack. I went on an internet quest to find online bokuto sellers that would give more of a choice in customization of length, style and wood composition of the sword. My search has yielded two pretty cool new sites that offer a wide variety of choices, or at least much more than we are used to having. The first website, "Blizniak's Bokken" is run out of New York and offers some of the most impressive choices I've yet seen. The website specializes in exotic hardwood bokken and even offers a composite "Dymondwood" material. A nifty feature of the site is that it allow you to use it's "Build a Bokken" feature to fully customize your sword. In addition they offer laminated bokken that allow you to combine up to three different wood types in one sword for a unique look and composition. They even offer Argentine Lignum Vitae which is essentially the hardest wood there is(they don't use other varieties of Lignum Vitae due to its endangered status). I just ordered a bubinga wood bokuto, and it should be interesting to test it out when it arrives.
The next site I found was bokkenshop.com, which offers a wide selection of bokuto in both standard and deluxe editions as well as suburito, stylized(bokuto made for specific sword styles) bokuto, lacquered bokuto and a myriad of accessories. They also allow for complete customization. Some of their bokuto seem outrageously priced but there are some good quality ones that are affordable as well. This company is based in Japan.
Both of these sites are seem like great resources if you're looking for something a little more tailored to your needs.