I walked into a roofing supply store and found, of all things, a 6
watt Weller battery-powered soldering iron (BP645MP). I had to have
it.
Turns out the tip itself contains the heating element. It attaches to
the body with a fitting much like an RCA jack. The soldering iron
works pretty well, and heats up quick as advertised. Of course you
can only use it on small stuff. Uses three AA batteries. Using it
very much could get expensive with replacement tips costing $5 each.
But it's a cool little toy.