Shaved ice flavor syrups
Korean grocery stores carry them too, so if you're near K-town, check it out. If on westside, there is a small (but great) Japanese grocery store called Nijiya (Sawtelle at Olympic) which carries it too. "Japanese" syrup flavors are usually melon, strawberry, maybe lemon. You can buy the powdered green tea and make a green tea one too. Yum. I think they're a lot cheaper than the Torani ones, but the Torani syrups have tons of flavors and are fairly ubiquitous (World Market, etc.).
More expensive flavored syrups in 750ml bottles are Torrani (about $4/bottle at Smart & Final and Cost Plus), Monin (about $8-10/bottle, at Surfas), and Sonoma (REALLY expensive, also at Surfas). These aren't what you'll find in New Orleans or Hawaii (although they do use Monin syrups at the shave ice stand on the beach at the Four Seasons Maui!), and theyprobably aren't cost-effective if you're trying to run a snowball stand, but for our home use we keep a bunch of different flavors around and enjoy mixing them up.
I prefer the flavors found at Marukai which includes the Malolo brand. Malolo has been around since time began in Hawaii and replicates probably the most authentic shave ice flavors around. BTW, the terminology used in Hawaii is called "shave ice" not "shaved ice" otherwise it's called a snow cone.
Check out Smart & Final. The one near me has several (really large) bottles of shave ice syrups.
Don't know where you are, but if you have a Mitsuwa or a Marukai near you they will carry Japanese shave ice syrups. 99 Ranch might have them, but I've never thought to look in the Chinese focused markets for this sort of thing.