ZWO have the ASI camera heater now available for ordering on their website, price is $19 USD, and more details are provided:
https://astronomy-imaging-camera.com...ti-dew-heater/
I have ordered mine.
Also, re the power for the heater, the heater kit comes with a Y splitter cable so the camera 12V power (normally just for the TEC) is used to drive the heater as well. The heater power output is 4.2W . The heater can obviously be powered separately if you want to . As long as your camera TEC power supply is rated at over 2amps (which is what the TEC needs) then it should be able to supply the heater element as well.