This site sells the nylon/spandex materials that rash guards are made out of. The cheapest solids I saw were $12.00 a yard, and I think I'd need maybe three yards at least? (two white, one black, and that's assuming I could find a way to use every inch without waste, at a guess.) If a sewing pro want's to tell me better, I'd appreciate it. Also, I think I could find it cheaper in a walk-in store, maybe.
Buy Ruffle Butts Pink Seersucker Ruffled Rash Guard Bikini at Sweet as Sugar Children's Boutique for only $ 26.50