My hottest port is at 85° so I wanted to try a fan.
These fit over the grill nicely but they slowly got louder and louder.
Dual 40mm USB Fan
I tried adding a pot and ran them as slow as I could but they still had a whine.
USB Fan Governor
I got this Noctua fan and so far I can not hear it and so far all the ports are 20-40° with the pot on the lowest setting.
Noctua NF-A8 5V PWM