I’m just curious but why hasn’t someone mentioned another option here, namely adding a power brick to the tender and PUSH the James engine around the track?
A 2 axle USA brick with the skates would give good power pick up or an AC cnetercab brick, could be fitted under the tender, and wire connections to the locos electrical pick ups would give the engine 8 or 10 place pickups depending on the block used, as long as the motor worm gear or the axle worm gear is removed and the motor wires on the James are cut, the eyes should still work the same, I would add some extra self adhesive tire weights on the inside to give the engine more stability as its pushed around the layout.