For sale is my Lincoln 140C small MIG welder. In addition to shielded welding, it can also use flux core welding wire. I believe you could also buy a spool gun for welding aluminum. It'll come with it a tank of Argon gas with a regulator, though it looks like the regulator may need to be replaced. I'm not sure how full the tank is. There are a handful of tips and wire feed wheels that I have for it as well (and an adapter for different sized wire spools).
It's been a great for my needs. I'm only replacing it since I've upgraded to a larger welder.