The pdf says the fan is ES, which should mean 'engineering sample'?I found this on alphacools site, seems to be newly released. It can go up to 10000rpm so should provide sufficient cooling. They give 36db at 10000rpm and its pwm. Its not cheap but if it does a good job and is more silent then the standard coolers in these things it might be a good upgrade.
https://www.alphacool.com/download/ENG_1020160_ES_40mm_400_10000rpm_Datasheet.pdf
How expensive is it?
I did a casual search and found this Fengheng 40x20 fan. At 10000rpm, it can push 10.5 cfm (~18 m3/hr) with 27 dbA. It is cheap (~3 to 4 USD).