As far as getting the original pieces:
-the manufacturer no longer sells packs of pieces (been years actually, so it’s not like you just missed it), just replacement pieces now a-days if you are shorted or receive incorrect pieces with the actual game.
-sometimes you can get pieces on ebay or the like, but often it’s cheaper to purchase a game and take the pieces.
-Field Marshal Games is working on a set of pieces to replace the ones that came with the Anniversary Edition, but they are still in the design phase. There is a thread in the A&A Variants Section below the individual games listing on the main forum page.
-there are some other companies that make AA sized pieces for different games, like Xeno, which are plastic and are considered cheaper than the AA ones, but on the other side are companies which make metal sculpts which end up being more expensive than a game.
really right now, probably best bet to get pieces is to buy a game.