My local Joann's here in LA has a truly dismal selection but, fortunately, there are some independent fabric stores, and shops that cater to 'the industry,' where there are tons of choices (literally walls of buttons displayed). Having said that, sometimes there are so many it's overwhelming or, once I've decided on one I like, will find out they only have it in sizes/colors other than what I need. One of the 'industry' fabric stores used to have huge boxes of old buttons...some carded, some not...for a fraction of orig price. Sadly, when they remodeled a few years back, they got rid of them. It was a fab way to find something unique for cheap.
And, I still keep a large jar of misc buttons from old sewing projects, tossed pieces of apparel, etc.