There's a thread somewhere discussing this, but I've been using Altitude Steel near Colfax and i25. They usually have a pretty decent scrap selection as well.
Horribly Painted '95 FZJ80 Has Some - Still Needs More!
"I drive an ECO-FRIENDLY FZJ80...It's got a salvage title which makes it a RECYCLED vehicle. Therefore, don't mess with me when I park in the "Reserved for Green Vehicle" spots in Boulder!!!