Look at the Holosun units, they're affordable, get good reviews, and they make the Sig Romeos. They make one with a 50,000 hr. battery life.
The Holosun stuff is the best value in rifle mounted red dots on the current market, IMO, speaking specifically about those models of the same form factor as the Aimpoint Micro (H1, T1, etc) and using the same mounts. Some of the Primary Arms models are actually Holosun products too.
