Do a quick google search for a local paintball shop. You may have one that you don't know about.
The issue with paint, specifically at Wally World - is that you don't know how long its been sitting, and how badly dimpled the balls are going to be. While test-firing and taking aggression out on a wooden post in the back yard doesn't require tournament paint...nobody likes cleaning out a barrel break from poor quality paint...every 3rd shot.
See if your field offers "airball only" paint. Its usually Valken Graffiti or RecSport or something of that quality. Its not great, but fields chew through pallets of the stuff, so the paint usually isn't 2-3 years old...collecting dust on a Wally World shelf.