I use an electronic switch (no moving parts) made by Seewater. I bought it from BoatUS for about $30, but I don't see it listed anymore. In fact the cheapest switch listed on the Seewater web site is now $500!
As a follow up, here is the response from SEEwater (too bad, a great product):
"We have discontinued the small units.
Thank you,
Ron MacDonald
SEEwater
951-487-8073"