Once you find a style of switch that you like, I’ve gotten some from drop.com when they were on sale for a decent price.
I’ve also had success with switches from kono.store
I think usually you can find switches usually sold in groups of 10, 35, or 70 depending on where you get them, and the price per switch can vary pretty heavily, anywhere from like 50¢ per switch to a couple dollars per switch.
I would highly recommend sampling a switch style or exact switch if possible before buying, though I have bought switches without doing that (after watching YouTube videos on them) and been mostly happy.