A few notes: if you buy non-module package (i.e MCU itself) then you would need to certify it with FCC (or you local FCC alternative) yourself, so most of vendors buy modules. Those vendors don't go to amazon to buy those because these make sense only if they manufacturing their own boards.

Last time I checked digikey had every module version avaiable for every version. You get hundreds of other versions because there are more variations of those.