Open source hardware, where you have the schematics, blueprints and such can be found at some shops mentioned at the bottom of this page:
Where can I learn more about open hardware?
We recommend checking out the Open Source Hardware Association's site, as well as Wikipedia's entry on open source hardware. Companies like SparkFun, Adafruit, and Lulzbot also supply parts and equipment used in hardware prototyping.
The best approach for finding hardware is to research the chipset beforehand, especially for wireless. If it's in the Linux kernel or there's source code available for it, it'll be open source / Linux compatible. Otherwise, it may need "binary blobs" from a package or may not work at all.
https://wikidevi.com/wiki/List_of_Wi-Fi_Device_IDs_in_Linux
I had success with this dual-band USB Wi-Fi adapter: