You need the OEM part -- aftermarket is not going to work.  
Hi, I have a Latitude E6420 laptop with the 0TYP01 heat sink + fan assembly (MF60120V1-C220-G99 fan part no.) that I believe is the 'discrete graphics card' version, not the 'integrated graphics' (?). The fan itself is starting to pack in, but I'm not that keen to spend £20+ to get the specific part (or basically the same for just the fan) on a laptop worth maybe double that, so I was wondering if there was any cheaper alternatives e.g. is there a fan with a slightly different part number that would work perfectly fine, maybe the integrated graphics version fan? Thanks for the collective wisdom
Latitude E6420 Fans