A contactor is a bit more rugged than a relay and usually set up for three phase switching complete with auxiliary contacts for interlocking or retaining etc, they also have the allowance for an overload to be attached.
You can pick up contactors fairly cheaply on ebay, new they are typically $300.00.
For a relay, you should be able to use the P&B PRD series, they have AC or DC coils and go up to 30amps.
They are reasonably priced around $30.00.
If you get the double pole, you can parallel up the contacts.