RE: Which compressor to buy?
A portable air tank connected to your compressor will give a bit of a cushion when spraying larger jobs. All it does, is gives you a larger supply to draw from. The down side is you need to wait longer for the compressor to catch up filling the larger supply. I would pull the supply from the gun off the portable tank. The portable tank will also help collect a bit of moisture.
IMAC, if your tank is still in good shape, you can buy just the compressor to replace your defective unit. Of course if the tank is bad, then things are a bit more sticky, but I'll bet a new tank could be had someplace.
Ken