I really can't provide any solid recommendations, but I can tell you my story if it helps.
Before I retired I used to travel quite a bit on the company's dime. I always kept my eye out for interesting bits of wood to support my pen turning habit. I had engineering teams in Israel so that's how I know my Bethlehem Olive Wood is the real deal, but that's another story. I also had occasion to travel to our corporate headquarters which was in Malvern, Pennsylvania. About a hour Northeast of Malvern in Sellersville, I met a fellow named Kevin Yardley who had a hand crafted furniture business. He hooked me up with some Cocobolo that was drop shipped to me directly from Costa Rica.
For around $300 I wound up with enough Cocobolo to make about 300 to 400 pen sized blanks. I picked through them and reserved about 70 of the most interesting pieces, i.e. the pieces that appeared to have some kind of interesting grain or color patterns or little knots and stuff. About a fourth of it had varying degrees of sapwood mixed in and I kept a few of the more interesting ones for pen blanks too. (I've made a couple and found I'm not really a big fan of the sapwood/heartwood combination). The rest was all what I would call run of the mill having a uniform color and straight grain patterns pretty uninteresting stuff.
I guess my recommendation would be to check with some of the higher quality suppliers of exotic woods like Bell Forest Products, Cook Woods, and Griffin Exotic Wood. Of course I would also check with the pen companies like Exotic Blanks, WoodTurningz, and PSI for their premium blanks as well. To steal a phrase from Forrest Gump, I've often considered Cocobolo to be like the box of chocolates, you never know what your going to get.
Dave