You want one of these I believe. 2 channels, fits your voltage range, R/C versions, BEC, fairly light. Notice they have several models under the Motor Driver section. Also lots of other gizmos that might be helpful depending on what all you are trying to do.

http://dimensionengineering.com/Sabertooth2X12RC.htm

If weight is an issue you need to consider lipo batteries. Much lighter. Or li-fe or whatever they are called if you need/want more safety. Still better than ni-mh.

Good Luck!