I have a pair of 3000 mAh 35C Wild Scorpions that weigh in at 12.5 oz each c/w connector. That was about as light as I could find at the time I bought them but Revolectrix now has similar batteries at under 12 oz., although that's without connectors. I've used them for only about half a dozen flights so I can't speak to longevity but I find that they're within 2 or 3 mA of each other when I recharge so I guess that shows some consistency of quality.
Where are you sourcing them? The place where I bought mine seems to have disappeared.