I have to side eye the controls and buttons and claiming that there's no market in the U.S. for them. There's three primary websites that we use in North America for arcade parts:
https://paradisearcadeshop.com/
https://www.focusattack.com/
https://arcadeshock.com/
Then there's the DIY and custom shops like
https://marvelouscustoms.com/ and guys like Vicko Mods
http://www.vickomods.com/ and Gummo
http://www.gummowned.com/
Not to mention large companies like Razer, Qanba, Hori, etc that makes arcade sticks.
Anyway, looks like the parts used were either IL or Suzo/Happ. I hope he went with IL because Suzo/Happ went to a Chinese factory a few years back and the quality of their products dropped as a result.
Checking the website that Linus used, looks like the stuff Linus ordered was the generic buttons and joysticks.
http://www.ultimarc.com/store/section.php?xSec=6