You're right.  The fans are this dimension (25*25*10mm) And it is 5V.

They're also available here: https://www.aliexpress.com/item/3d-printer-part-fan-2510-2pins-25mm-25x25-x10-mm-2-5cm-graphics-card-fan-DC/32810831724.html?spm=a2g0s.9042311.0.0.67a74c4d9mHuRe

I got some of these, they are not any more or less noisy than the stock fans. Actually the more quiet and effective solution is to buy a strong silent USB fan (the round tube ones) and use those instead of the stock fans. But YMMV.