I haven't purchased flints for longer than my memory. which don't mean nothing cause i can't remember supper.
October Country, Track of the wolf, Muzzleloaderbuilders supply, Dixie gun works and probably 50 more all sell good English, French flints.
buy a node of Georgetown off ebay and learn to make your own. satisfying and after a couple years the cost will even out. If you don't cut a major artery.