A search for "naturally carbonated" returned http://www.finewaters.com/Sparkling_Water.asp as its first result. That site mentions Apollinaris, Badoit, Gerolsteiner, Wattwiller, Ferrarelle, and Borsec. San Pellegrino's a famous water that's a borderline case -- the CO_2 is added by mixing in "naturally carbonated" water from a separate spring.
You could try and make all those acceptable answers, but it might be easier just to adjust the question to make it unique to your answer. For example, "Water brand bottled from a naturally carbonated spring in Vergèze, France". |