The charms are available in each resort gift shop (moderates & deluxe anyway, I'm not sure about the values) & each of those shops has a charm, specific for that resort. When we stayed at Caribbean Beach last month, we were able to get a CBR charm. My DD11 & I each got charm bracelets. I made mine a Hawaiian theme - I got the CBR charm, a palm tree, Lilo with a surfboard, & a few others.
Besides resort gift shops, the charm displays are found in several of the larger gift shops in all of the parks. There are dozens of charms to choose from.