Get in touch with your local forestry dept., tell them what you're after and why, ask if they know of anyplace/anyone who may have some osage or other bow wood to cut. I did so, and was immediately put in touch with a very nice couple who allowed me to cut a big osage tree on tbeir family homestead with the condition that I make them a selfbow with the wood from the tree.
I've also been hooked up by contacting arborists and sawmills in my area on occaision and asking them to let me know when they find something I might use.
If I still couldn't find any, I'd hang ads in grocery stores, in the local papers, traders, craigslist wanted, whatever it took.
Put your feelers out. You'll soon have plenty.
