Vine maple is very easy to find.
Infact, I bet once someone confirms you have the right tree. You'll be shocked you havnt noticed it before.
Stever Meyer of Little Hindu forge, is a hell of a nice guy and decnt bowyer in his own right. I bet hed give ya some help.
Also, the is a 3d shhot in Topponish this weekend. You should attend, there is a large self bow community in WA. The TBW club is rather large and certainly worth being a part of.