I actually found a listing for bear arrow spines on one of the threads here , Go back through the old threads and I'm sure you'll find it . I recieved 6 magnum 308 arrows with a old bear spring arm quiver I got on the auction site. They were all staight and with good feather fletching so I decided to try them through my Takedown @ 50# They gave me the best arrow flight from all that I tried (limited trials mind you) So I hunted with them this year and will be looking for more in the future.
good Luck with em
Dean