New Digital 300 Watt Hardside Waterbed Heater with a 4oz Premium Clear Bottle Conditioner & Patch Kit For California King, Queen & Super Single Water Beds

This is a very popular choice and it is very easy to use. It also installs to most older model waterbed with ease.
If you want a heater which can pin point the exact temp then this is an excellent choice.
*Certified to the standards of the Underwriter's Laboratories for Waterbed Heaters.
* 18 Gauge power cord.
* 32-guage Nickel/Copper flexible circuitry
*Larger Pad with 64-guage Thermal Fused D