Amazon.com: CPU Cooling Fan with Heatsink for Lenovo IBM ThinkPad T420 T420i 04W0408 UDQFVZR01FFD 04W0410 04W0628 : Electronics
T420 CPU upgrade to i7 2860QM quad core. Paste is Thermal Grizzly Kryonaut. More info about upgrade and passive cooling upgrade in comments. : r/thinkpad
New Original For Lenovo Thinkpad T420 T420i Swg Discrete Graphics Heatsink Cpu Cooler Cooling Fan 04w0408 04w0410 0a66707 - Laptop Cooling Pads - AliExpress
ThinkPad T420 CPU Upgrade (i5-2540M to i7-2670QM) - YouTube