Just was looking for very low noise fan replacement for my PS2 and CPS2 and what do you know Noctua released the perfect fan for CPS2:
https://noctua.at/en/nf-a6x15-flx
Airflow is 23.4 m³/h (13.77CFM)
Acoustical noise 19,8 dB(A)
The current replacement fan I have in CPS2 is a Sunon...