you can generally get one used. I purchased mine used up here in Canada from a place called Bill's Trucks (
http://www.billstruckshop.com/). Bill's a great guy and will get you what you need, that said, you're in the US and should be able to source one more locally (there are tons of Chevy's in the US).
I think i paid $75 for EVERYTHING (Shipped to my door). Sure it was used, but i got the support member, threaded rod, bolt and securing nut. I've since installed it and there are factory bolt holes for it in the frame. I hated having my spare in the bed all the time so this was great (and cheap).