Is there a charger that can charge it from the outside threads?
Not that I know of.
Are your threads completely bare? No traction whatsoever? Can you attach your battery to the charger and perhaps secure it in place with a rubber band? You could try one of those spacers also--just drop it into the 510 well. All you need is electrical contact--center pin to center pin--in order to charge your battery.
Circuit Board Spacer
Your battery comes equipped with dual (510/eGo) connection, you can use eGo threaded heads on it bypassing the 510 threads (and vice versa). As long as you make electrical (pin to pin) connection, your atomizer will fire.
If the outside (eGo) threads are OK, you may also try this eGo-to-eGo/510 adapter. I'm not sure why Spaceballs doesn't recommend charging via an adapter--maybe he knows something I (and my learned colleague Kent C) don't know...
EGO to EGO 510 Atomizer Adapter : L Js E-Smokes, Electronic Cigarettes
Having said that, I have owned several eGo-class batteries and never had an issue with stripped threads. Are you using good batteries (Joyetech, Vision, eVod etc.) or cheap knockoffs? Also, if you're using huge 510-threaded tanks on your eGos, at least secure them with a beauty ring. eGo-class batteries were not originally designed to be used with heavy 510 tanks and they may be stripping your threads--especially if unsupported.
Bad for your threads:
Good for your threads:
Good luck!