You won't find it at any local stores. Liquid Splenda isn't legally sold in the US, except to food manufacturers. Anyone who is selling you liquid splenda is selling a black market item, and it's with the disapproval of the sucralose manufacturers.

That being said, liquid stevia is something easily found at health food stores, and I've used sugar free DaVinci syrup as my sweetener in lots of recipes to keep the carb count lower.