RC toys can break just like any other gadget, and if you need a new speed controller, this might do the trick.
From Appliance Electronics
Hobbywing MAX6 ESC Combo With 5687-1100Kv Motor HW38010802
Model Bau
Hobbywing Combo Ezrun Max6 Esc 5687-1100Kv Motor (Black) HW38010802