I remember reading an article when they were starting up, snd the founder basically went to some expo in a China and purchased OEM devices and slapped his brand on there.
Edit: This isn’t the article but it sheds some more light.
> Once he had the strap sorted out, Woodman would need a camera to go with it. He eventually found a 35-millimeter model made in China. Woodman made an old-school prototype using a Dremel tool, plastic blocks, and glue. He mailed it to China, wired $5,000 to get started, and in September 2004 GoPro made its first sale when a Japanese distributor ordered 100 units after seeing the product at a trade show.
https://www.maxim.com/gear/gopro-founder-nick-woodman-profil...