NAD T765 AVR replacement fan?

I have a bad fan on my T765 that whirrs loudly upon startup until after a couple minutes, it slows to a halt.
I don't know how to determine what replacement fan to get (manual does not mention, Google failed me).
I also have a T775 that may have a fan that's going as it started to get noisy the other day.
Any advice on which fan to get, and where would be very much appreciated.
You could take it apart and try vacuuming first. 
Probably worn bearings. Try flipping it 180°.
Thank you for the prompt and thorough response, imhififan. I ordered a couple of those fans. I looked in the service manuals and note that there are 2 different fans, 330mm and 430mm. I am not sure if this is plug length or what, but I noticed the linked Amazon ones have what appear to be shorter cables. I hope they work/fit!
Sorry I didn’t mention it, but I already tried cleaning. Flipping the fan I would think would defeat the purpose of the adjacent fans as they’re all forcing air in the same direction.
Really cool how supportive this community is - I can’t wait to get back into HiFi now that I have a domicile to support. 
I used to replace the fans in our old CPU's.

If I coudn't find one with the same connector (or needed wire length) without paying a high premium I would just splice the wires from the old fan onto the new unit.

I would solder and wrap them, but a tight twist (or wire nuts) and electrical tape might be OK.