Only soda "extract" they have that I know of is for soda stream. If they had any it would be in the house wear department (pots, pans, etc) near the Mr. Beer packages.
Try a Meijer also. I am certain they have soda extacts, at least in my local one.
Its like a walmart but with a bit better quality products and more prevalent than walmart in Michigan.
Your Walmart has Mr. Beer packages? That's pretty neat. Never seen them at Walmart before.
Rocketsan, What part of the US are you visiting? Most of the Walmarts that I've seen here will have a wide selection of the Watkins brand and very good prices. Is that what you picked up? Most that I've tried are decent flavorings, but I don't like the cherry flavor. I have seen almond (good), vanilla (ok), coconut (very good), banana (good when fresh), cherry (tastes like nyquil), chocolate (good, but tastes like tootsie rolls), orange (haven't tried), root beer (haven't tried), peanut butter (haven't tried), butter (good), maple (good), anise (haven't tried), mint (good), peppermint (haven't tried), raspberry (good), strawberry (haven't tried), caramel (haven't tried), and maybe a couple others that I can't think of at the moment.
If you stop by a kroger store (Kroger, Dillon's, Fred Meyer, Ralph's, Frye's, King Soopers, Smith's, etc.), I know I've seen some different extracts under their store brand there in the baking section that I've not seen other places. Though the only one I can think of of the top of my head is brandy flavor.