Okay Daddy Warbucks, get out your wallet and let's get busy.  You probably don't have the time, desire or abilities to make your own stuff so let's stimulate the economy instead. 

I must make it clear I am not endorsing any of the vendors below.

K & C Custom Painted Trains
haddow28@gmail.com

Henson's Train Emporium

The Milwaukee Road Train Shop (highly recommended by Jeff McCrea)

Robert Engelbach custom makes and paints Alaska Railroad gondolas, diesel locomotives and cabooses in HO scale.
 
 

Thanks to Casey and Pat Durand, Curt Fortenberry, and Randy Thompson for providing this information