a law Enforcement supply website, but you're basically looking for "BDU"'s, which the public can purchase. try to buy a badge and they're gonna want some credentials. But Ive bought BDU's from there. Good prices and nice selection.
Also Army/ Navy stores in your area have genuine new and used BDU's. Most range around $40 / pants and $30/ shirts. BDU jumpsuits can range around $100