There are other brands:
Accutorq 220SG Mini HV servos. I thought I read somewhere that these are made by KST?

KST X15-908 HV Mini servo. I have used the X12, X10 and X08's from KST with good success.

Kingmax has a 15mm sevo under $30, if you can find it in stock. CLS2875H

Bluebird has a few 15mm servos, the BMS-A921 has 10kg torque and is under $50. I'm trying Bluebird for the first time in a small glider and so far they seem very smooth and quiet.