Doing a little bit of searching online for other sources of ebony fingerboard blanks:
There's a place selling on ebay called Exotic Wood Zone. They are apparently in St Louis, and they have a supply of fingerboard blanks in exotic woods. Not cheap. But it appears that they know somewhat what they are doing in preparing and storing fingerboard blanks. Macassar ebony bass size are $40, Gaboon ebony are $70.
Search "fingerboard ebony bass".
I don't know anything else about them. Has anyone bought from them?
Edit:
Here's their own web site:
Buy Exotic Woods | Best Lumber Dealers in USA
Wow! They are a full serious Luthier lumber company, a competitor to LMII. I don't think I've heard of them before. They've been in business about 10 years, supplying exotic woods to musical instrument manufacturers. They have the sources, do their own milling and drying, and have a warehouse full of stock. Okay, that gives them some credibility.
I'd say that they are now my first choice as a new source for ebony. fingerboard blanks.