Seeking advice for replacing bevel gear for V3 gearbox
 

I bought a APS AK74. Just after a few auto-shots, the gear box did not work and only the motor revolved. After I disassembled the gear box, I found the issue. The bevel gear broke as shown in the photo. I cannot imagine how weak the bevel gear is.
As I don't have the knowledge of gears, now seeking the advices for the replacing bevel gear or the whole gear set with reasonably low price.

Thank you, guys.