The place is called Eidnes Furs out of Idaho or Utah, one of those states. I have gotten pretty good service from them. I don't think they offer moose sinew, where do you get moose.
I've get about 4 pieces done so far, (coarsely done).
I also got some bear rawhide. It's pretty thin. I'm hoping it will make good backing for a pecan board bow.
Also, I've research natural pigments again and have come up with a load of good info. I want to "paint" the back of some bows including this one. Blood makes a nice red on sinew.