You'll have to do some calling around, but some of those old lots aren't shipping off thier stuff for scrap because they lose too much in fuel charges. It's a matter of sniffing them out, try looking up local car clubs on your travel route.
29 Palms is a bit more East than the places I know of, you may try some of the blaces outside of Barstow, West into the area around Edwards AFB, and North into Ridgecrest and NAS China Lake (there's a few old scrap piles there that make me drool).
Also, on the other side of the Rockies, my dad has been findin all kinds of old bolts in KS north of Topeka. Keeps teasing me with photos tha jerk!
