I've had positive experiences with JPs Corner.
I know that other members on this forum have too.
These tend to be a bit thicker than some alternatives.
Sometimes people prefer thinner plastic or white rings...
Here is the listing that I've been purchasing through: Link
In case the link disconnects in due time:
eBay Listing Title: "15 Air-Tite X43mm Ring Coin Holder Capsules for Coins Less Than 3.96mm Thick"
eBay Username: jpscorner
Provided Stock Image: