Followup:
The ERR RailSounds Commander PA Diesel kit arrived today and I installed it, along with GRJ's YLB, in a recently acquired Williams FA-1. Yes, the ERR RS Commander is expensive, but it does sound good and I am quite pleased with my decision.
FWIW, here's my ESD-safe kit for working on circuit boards. Using painter's tape to secure it, I make a work pad from two layers of aluminum foil—a large rectangle folded in half. The alligator clip is afixed to the aluminum foil and the copper clamp to a grounded pipe.
