Where to buy premium names:
Afternic, BrandBucket, NameCheap, Sedo, Dan.com, Godaddy Auctions, NameJet
Better way to find available domain names:
Searches all possible variations and relevant extensions, including premium. This way, you don't have to type in the exact domain and every possible variation every time you have a new idea, and you don't have to search in multiple different sources. Each registrar only supports some extensions, not all of them. Besta.domains searches ALL possible extensions, but narrows down the ones that match your keywords.