I’ve found a drop in metal gear replacement for Hexy’s servos, the Turnigy TGY-50090M.
I’ve successfully replaced all the servos in the back two legs and they’re working great. Unfortunately I didn’t order enough to replace everything because I wasn’t 100% sure they would fit, so I have to wait for the next shipment to replace the rest.
It was a little tedious replacing the servos. The gear is a little longer in these servos so you need to install the servo horns that come with them instead of using the horns from the original SG92R servos. Otherwise, the servos seem to be an exact match.
These servos give more torque and faster movement, especially at 6v. Based on my experience so far, I would highly recommend them. I am getting much less jitter and the increased torque is a noticeable improvement.
You can get them on Hobby King for $4.99/ea: