Truckracer-
The directions that come with the Rcexl opto switch show how it can be converted to eliminate the need for a separate battery lead. Direction .pdf included, chinglish terrible, go to the bottom of the directions and look at the before and after pics. Basically, all it does is switch it over so it's powered by the same lead that's used to turn it on and off. There's other ways of doing the same thing pretty easily as well.

Also, Valley View sells the Rcexl switches with a BEC. I don't know if they are doing that same mod in house, having them done, or have found a source for them.