Most people who manufacture those small welders will supply what you need to run a gas bottle and solid core wire, and call it a "kit" The kit consists of a gas regulator, a different set of drive spools because the wire used with a gas bottle is smaller than a flux core wire, and an electric solenoid that turns the gas on when you hit the weld trigger. Some of the real cheapy welders don't even offer a kit to convert to gas, so as Ceh383 sais, check this first. If you can get the kit (or if your welder already has the right stuff, then don't screw around with your local hardware store or Wal-Mart---Go to a registered welding gas supply house and tell them what you want to weld, and let them recomend the correct gas. You can buy the gas bottle outright and just pay when you have it refilled, or you can rent a gas bottle on a 6 month or 1 year contract..