Google paintballohio.com. Call them they are in Columbus.
On the east side of Columbus is a place called "general merchandise" that sells the cheapest paint in Ohio. I've used them for hydro, but they wait for a few tanks and send in a big order. Mine took a couple weeks from G.M., but only cost $30 out the door with reg removal/replace and shipping.
If your able to remove your own reg I like to just use hydro tester as listed above.