The first place that popped into mind is to contact an open minded person at a large Zoo in your area. That should take care of the mammal stuff. The tree ash, now that's a tuffy. A parks person may be able to help direct you there. Does the obsidian blade need to be an artifact (need to have been a real spear/arrow head) or can it be a tear drop obsidian? You can order these on the internet or better yet, pick one out your drawn to at a decent rock and gem shop.