I have not seen anything local to be honest. I bought mine from a forum member.
Definitely Pebble Junction in Sanford they have a pretty good variety too.pebblejunction.com, its in Sanford. You can look at what they have on the site... going in person is better though as some rocks look different depending on size.
Pet Bazaar in Casselberry has some ok looking rocks too, but they are $2-3/lb :/