SASA is the most popular, it’s good for large hauls, but I typically purchase from Adambeauty because the shipping is so cheap and they have competitive pricing. SASA stuff can be expensive or sold out a lot of the time. Kiwi-Berry. There is also Pretty & Cute. And as always, eBay.
For circle lenses, Soompi has a whole forum dedicated to lenses, including reviews of the lenses and reviews of shops that are well-rated. I always reference there when I’m considering getting circle lenses. And here’s a great list of online sellers - click! Personally, I have bought circle lenses from Pinky Paradise and Kiwiberry.