I had one of these laying around. It’s a drop-in replacement for the stock fan and is nearly silent.
http://www.mini-box.com/Noise-Blocker-XM2-40x40x10mm-Case-Fan
To stress test, I’ve set my MacchiatoBIN to run at 2GHz and have four instances of this cpuburn running
https://github.com/ssvb/cpuburn-arm/blob/master/cpuburn-a53.S
After 60 minutes the temperature hovers around 67C (up from 50C at idle) in a room that is 23C. Power consumption is 19W (including 4GB RAM, 120GB SATA SSD, and 1Gb ethernet). There’s been no thermal throttling.
