A nice touch is the 2956026 EMG 17-REL/KSR/120-21, which snaps in with no fuss during setup.
DC 6V24V Double Pole Double Throw DPDT Relay Module SelfLocking Switch
If you want something simple, the Honeywell RA8366 does the job without fuss.
A nice touch is the clear datasheet notes, which help you understand the relay behavior before you finalize your wiring.