The Boeing RR Club in St Louis has 2 swap meets (shows) a year. They have almost 300 tables of RR "goodies" from sellers from all over the mid west.
http://www.zealot.com/forum/showthread.php?t=172961
At the last Boeing swap meet I picked up these 4 CB&Q Reefers with KD's & metal wheels for $12 ($3 each). So today I did some quick weathering with India ink & chalk. (I now see after I took the photos that a couple of the cars are off the track!)