To charge/balance 2 packs at once you will need to make a "Y" harness that will effectively wire the 2 packs together in series through both the balance leads and the main power lead. Then you would charge/balance your two-2s1p packs as if they were one-4s1p pack. I think Robert Green has an article demonstrating it on his DIY site. His article describes two-3s1p packs but translating it to two-2s1p or even three-2s1p packs, is just a matter of common sense. Google 'Robert Green DIY' or something like that.

Align to TP balance adapters are available all over the net and probably available at your local hobby shop as well.