You would need to define exactly what you mean by "cheapy". If its not saltwater safe, your only going to be able to use it a couple of times before it will start throwing rust into your water....
I would recommend buying a mag that is similarly sized to your current return pump.........two birds with one stone...back up return should your current one fail and will mix the heckout of your salt.
Most systems can easily be set up to run the mag temporarily out of your sump even if you usually run a
external return pump......
