RC toys can break just like any other gadget, and if you need a new speed controller, this might do the trick.
From Amazon
Hobbywing HW30120201 Accessories for Remote Control Models, Black
Model Bau
Hobbywing Quicrun 1060 Brushed SBec WP ESC (60A) HW30120201
Conrad Electronic
Hobbywing QuicRun 1060 60A Model car brushed speed control