Mike,
I use the Kendrik dew heating system with the dual channel (four output) controller. This gives me four dew control heating strips to use. There are a number of heating strips available and I use two types, ones which are designed for the 2" eyepieces and larger ones which are suitable for refractor OTAs.
I find that the heating strips designed for the 2" eyepieces work fine on the lens of the camera. By wrapping it around the lens before focusing this seems to work fine. With the controller supporting four dew heating strips I have enough for the camera lens, the front of the guidescope, the finder scope and one spare. The controller takes a 12v input with the standard car cigarette lighter plug.
Link to the Kendrick site showing the dual channel controller is here:
http://www.kendrickastro.com/astro/d...ardDualChannel
The link to the information on the heating strips is here:
http://www.kendrickastro.com/astro/d...erheaters.html
Only cautionary note is that they do consume a reasonable amount of power so a good size battery is in order. I have a 18AH gel cell battery I use in the field and a back up in case I need it.
Hope this helps.
R