Actually I just remembered Matheson Gas sells welding gases. They should be able to fill it I think.
MATHESON-South East Zone
216 S.W. 28th Street
Ft. Lauderdale, FL 33315
http://www.mathesongas.com/
I dont have an answer for you on the CO2. But as another Fort Lauderdale resident who just got into homebrewing, are there any local home brew shops in this area you prefer?