Made a frame mounted plug in using a trailer light plug and hose clamp. My chargers aren't the Battery Tender brand but I believe it is the same plug. If so, the plug will work on, and only use two of the four plugs of a flat trailer light wire. I sawed off the unused plug ends giving a place for my hose clamp to hold it to the tab in front of the helmet hanger.
I did put an in-line fuse in the hot wire, could have put a small hose around the hot wire under the fender to better protect it, did cut the wires off of an extra plug just to cap it off and keep dirt out while riding.