Get a buck converter to drop the power supply voltage for whatever fan you like. If you compare the Noctua volume flow rates to same-size normal fans you'll see they are lower. Noctua has some fancy bearing technology, but I believe the reduced speed/flow is what gives the bulk of the noise reduction. You can operate 24V fans from much lower voltage and they will turn slower and much quieter. So, an adjustable buck converter and a 24V fan should get you a lot of the noise reduction you're after.
Many 24V fans will run on 12V, but may not start reliably, so you may need to give it 15V to ensure reliable start-up.
Here's a 6-pack of adjustable buck converters for $8. Once you have them, you'll find all sorts of uses for them, from running fans to powering LEDs, etc.
Ultra MegaMax Dominator 3D printer: [
drmrehorst.blogspot.com]