It's doubtful that the FA would know what brand of toppings are used for the sundaes. The caterer (Gate Gourmet) would know. For Foodservice & high volume kitchens they come in larger containers, like a number 5 can, which is approx 3 quarts. Aside from that, it's hard to be sure what brand is used, it could be a generic Sysco brand. I would place my bet on Lyon's, as they have the main grip on dessert sauces and toppings. Good luck getting these, they don't really sell to retail consumers, but you can buy at some warehouse retailers like Smart & Final.

http://www.lyonsmagnus.com/fountain_gourmet.html