if you can sew, jo-ann has a lot of patterns and fabrics for cheerleader outfits. sometimes they even have stitch/iron on patches that'll say cheerleader-esque things. always look at a costume store, and not just the ones that come out with all the crappy bag costumes every halloween. look up costume shops in your area online or in the phone book and check one of those places out. they usually have a ton of variety in a billion different things where you could possibly buy or rent your costume from them.
good luck :3