I have been looking for the same thing, I still have found nothing that will fit in those mini p/t domes, how cold does it get there? here it drops down to -45c at times without the wind. I am not sure that the unit would stop working do to the cold. I do know that starting the p/t camaera in a frozen state is not good, I tested one at -30c and it locked up and the video failed, once I warmed it up, the pt part recovered without a problem. in the end the cameras video board was lost. I sent a letter to the company that makes the camera, they told me that they would look into the probem.
Four days later they sent me a new spec sheet on the the dome with a -35c rating
I am expecting a new shipment of them this week, I will let you know if they came up with a mini heating strip.
empak