Originally Posted by TK421
where do you buy them tho
Nowhere, don't need such fans. But other people buy those Nidec GTs, Deltas, etc. somewhere don't they. Or sometimes you can get samples or your company can get samples, etc. Some electronics parts (not computer parts shops, but shops where you can buy resistors, capacitors, inductors, wires, cables, connectors, transistors, ICs, fans and all other DIY or repair electronics parts) shops may sell such fans but this highly depends on what fans/brands a shop wants to offer. Locally for me the two major (or old known) shops sell SUNON fans, not Nidec. A different fan maker, with a single type of fan having a 90 page catalog of models and specs to choose from.
Those Nidec GTs are often resold for profit by someone who bought a lot of them, so they put them up on Amazon, eBay, ... Yeah those coolerguys from Amazon have a store linked above, there is a 38mm screamer too, just a restickered fan made by someone else and plenty other brands of fans in 38mm.
Nidec makes a crap ton of various fans.
If all else fails you can always get most stuff from Aliexpress, Alibaba, etc.
Yep, Nidec 120x38mm 5300rpm right there on Aliexpress. Not that hard to get, half the price of 1 Noctua fan, shipped. If you must have a 38mm screamer.