Numerous third party accessory and peripheral manufacturers create controllers and more for Switch. Some of the products are great, and others aren't so hot. It's always a crap shoot with third party efforts, but in some instances, your only option is the first party outing.
That's the case with the Ring Fit Adventure Ring-Con, which is only made by Nintendo. Rumor has it that a Chinese manufacturer was trying to make their own Ring-Con controller. We're not sure if they planned on selling as a legit replacement or a knock-off, but either way, it seems the project isn't moving forward. Apparently the manufacturer involved with actually replicating the Ring-Con failed in their efforts, and the project was scrapped.