i usually get my beads on sites like amazon, but if you're not able to find anything you'd like there, aliexpress has TONS of cheap beads and charms. you can also probably find stuff on temu, hobby lobby, or joann.
for hobby lobby, if you're looking for pony beads, i recommend looking them up online to see if they're available in a store near you. they usually sell beads made for more regular looking necklaces and bracelets, but if that's what you're looking for, then you're in luck! ^__^
hope this helped!