The radioshack relay you would want would be this one:
RadioShack Relay 275-218
Then any 120VAC switch (that handles enough current). Apparently relay price has gone up since i purchased. But any 12V switched relay will work fine, in parallel with a switch, to do exactly what you want.
Example switch:
RadioShack Switch 275-666
Note that this switch can handle 3 amps at 120VAC, and the relay is good for 10 amps at 120VAC. Both are extreme overkill (power handling wise) for this project (running a pump that uses what, 20 watts = .2 amps at 120VAC) but thats not nessesarily a bad thing. If you can find a cheaper relay/switch that more closely meets your power requirements, then go for it.