Call Brake Buddy and ask them for a 12-volt kit. Receptacle, wiring, fuse, terminals. Makes the BB outlet hot all the time, and with enough capacity to run the BB well. Wire it on the battery side of your disconnect(s).
It carries a price, but I've never heard of them billing for one when you call support and tell them you have it in a late model vehicle. The old "Lighters" were wired heavy enough to run a BB. The new 10-Amp "Outlets" are not. BB will send the kit rather than have you calling back with trouble. This pic shows a plastic socket. I think they send only metal ones now. If you get one with plastic, cut your losses now. Go to the auto supply and get a metal one.
If I have a good (I don't mean expensive or special, just not a failing one) battery in the toad, I can tow all day. A "charge line" isn't a bad idea. Just that I don't have one and have never needed one.