I´ve tried the Khadas Fan Kit, but for me it´s still to loud.
I found this simple solution: https://www.amazon.de/Arctic-Breeze-Mobile-USB-Ventilator-Kühlleistung/dp/B00KBO5Z8C/ref=pd_lpo_vtph_60_lp_t_3?_encoding=UTF8&refRID=SJAW0YF9MEK87J96A3CT&th=1
…also available on alibaba and ebay…
This fan is quiet and you can also change the Fan Speed. Works well!
Have you installed the Eva Washer provide together with the cooling fan set?
With and without the EVA Washer. The Arctic is absolutly noiseless. For me the best solution.
We have new solution, just mount the fan on the Heatsink: