Jim,
They sure do. I don't have any first hand experience with these but they look like a good solution.
<A target="_blank" HREF=http://www.houseneeds.com/shop/HeatingProducts/WaterHeating/t-k1/t-k1.htm>http://www.houseneeds.com/shop/HeatingProducts/WaterHeating/t-k1/t-k1.htm</A>
I went electric partially due to the sticker shock! and partially due to the fact that I got the biggest electric one I could find in order to act as a water storage tank for my well system.
Fred