I've got a fair amount of back sinew, including lots of long pieces. I do a very good job of cleaning the membrane, meat and fat off the tendons and give them a very thorough degreasing before I dry them, so they're easy to process and will stick to the bow's back well with most any adhesive. If you want to figure out a trade, I'd be open to that. Just send me a PM.
That's an amazing stave, by the way. Some of us would about do a backflip to acquire something like that. Turn it into something pretty!