I have installed RailPro LM3g units in all my locos (6 so far). I got them from Remote Control Systems of New England. Don Sweet runs the shop, and he is very knowledgeable indeed when it comes to RailPro. I'd give him a call and ask him (603) 321-1347.
I did the install on my locos, I found it a little tedious, but enjoyable. The results are fantastic - operation is excellent, sound is phenomenal and the joy of not having to clean the rails is beyond belief great.