Could any one suggest an alternative capable of providing the charge necessary?
I'd suggest that you think about where the servo you are using was intended to be used. Most likely, the place you got it from also sells RC cars, trucks, boats, airplanes, and helicopters. You'll notice that none of them use 4AA batteries. They use big, rechargeable batteries.
Why? Because servos need a lot of current, and 4AA batteries just can't provide the needed current. Look at the batteries available from the same vendor you got your servo from, and pick one of them. Matched to your servo's voltage and current requirements, of course.