Circuitron
End-Of-Train Flasher

Red Light
Walthers Part # 800-1302, p. 773 Walthers 2012 HO Scale Reference
A scale, $16.95, currently in stock at Walthers

 
Scale size housing, easily mounted on any freight car. High-intensity LED slowly flashes a bright light rearward. Requires 3V input, easily obtained from two small batteries; the TP-1 Track Power (#800-2001), can be used if the car is equipped with track power pickups.