Radio shack would probably be the easiest. This one would be perfect, and it's carried in their stores: http://www.radioshack.com/product/index.jsp?productId=2062523
You can find something similar at any auto parts store, or home improvement stores.
If you're using it with your amp's remote wire (by far the best way) then you don't need anything heavy-duty at all. The remote wire current is so low that just about any toggle switch can handle it without a problem.
Look for a SPST switch. You can use a lighted switch if you want, but it will be more difficult to wire, and you'll need to find a voltage source other than your deck's remote output.