Hobbywing made FAN-2510BH-6V-18000RPM@6V-0.27A-BLACK-A 30860004 (HW-30860004) Cooling Fans Motor / ESC / Cooling Fan
With this particular fan installed on your ESC heatsink, you should have the optimum cooling performance.
Specifications: Ball Bearing / Non-waterproof / ZH Male Plug / L=38mm
Applications: XERUN-XR10-PRO