That's what I would have guessed at first since it would be a silly
thing to make proprietary, but nobody was mentioning a fan measuring
92mm x 92mm, even the OP, although someone else mentioned size of retail
packaging. I don't think my measurements are that bad,<g> but some
catalogs did mention 90 x 90.
Well.. I just have mentioned them. They are a standard item
in most any fan manufactuer's product lines, available at
most full-stock 'sites that sell fans, and come in almost
every configuration that 80mm fans do. They are not "as"
common as 80mm, but common enough.
Fans or personnel? Sure, but when they're dealing in that sort of thing
on a daily basis, you'd think they would say simply that they don't
stock that size and try Joe's down the street for that one. As I said
before, it ain't rocket science.
They don't usually replace 92mm fans on a daily basis, as
OEMs were more often using them and (usually) used decent
enough fans that they don't fail within the (rest of the,
component or useful) life of the system.
How much stock would they keep? Some shops do have 92mm
fans, others may not at any given moment or at least not
every possible speed and connector. Usually it doesn't take
long to order and receive a fan and they're not hard to find
so there may be limited need to keep that kind of stock,
especially since most people don't pop in trying to buy one.