I searched MTH website for an appropriate tender to run with my PS3 Railking J engine. I found that currently, 30-79497 and 30-1117 are available but use thumbtack couplers, with no note if backup light equipped. The 20-3134 and 20-3619 are proto coupler equipped, and the 20-3619 is noted for PS3 engines (guessing backup lights are LED, not incandescent, and a wiring harness hookup to PS3 boards) only.
Odd that the 30-XXX tenders don't have proto couplers (cost point or wiring hookup incompatible?) Guess if determined, could swap out for proto coupler and harness to run with Railking PS3 J engine (I am assuming Railking PS3 boards are same as full scale engine boards).