Not sure if it qualifies as scrounging, but I've found lots of nice "detail" parts at Ace Hardware.
Brass rod of various sizes to simulate the HEP connections. Pretty rough in the raw form.
The strobe units on this are the joint sections I cut off of very small plastic tubing. I put an HO scale strobe unit in the loco with grain of rice bulbs so these slide nicely over them.
Similar approach to finishing out the cab car: