A while ago I changed what I was doing for dew control. What I was using originally was a secondary dew heater from Kendrick and while that worked, because of wire routing, it did bad things to my star shapes. I switched over to the following system some time back and it has worked quite nicely.
The Pyramid PS15KX 10A 13.8-Volt Power Supply with Cigarette Lighter Adapter is currently available from Amazon.com for 59.37$. I image from my observatory so a power supply like this makes sense.
The SDCC Two channel/four output standard dew heater controller is available from Astronomics. Currently it is priced at 114$. This is a basic controller but it gets the job done.
Last but certainly not least is the Dew-Not Dew Remover model # DN09. It is currently available from Agena Astro for 44.75$.