Honestly, I would not expect MRC to be very forthcoming with a part like that (or any part for their steam locos).
It looks like it could be soldered back together pretty easily. Just tape the two parts down firmly on a piece of wood,
apply a dot of flux, and solder. I'd suggest adding a thin bit of brass strip across the joint and soldering that on as
well to it won't flex and just break the solder joint off, which will surely happen eventually without that splice reenforcement.
As for improving the system so the wire doesn't break off from the pickup strip, below are two photos where I modified it so that the wires that come down through frame no longer solder directly to the pickup strips, so you can take the gear cover off without the strips breaking off from the wires. This was from the early generation MP engines. I don't have any of the newer ones, but I assume the same idea would work.
This modification required delicate soldering, but it definitely worked well.
