Hopefully someone with more experience will give you something more substantial than this but depending on his enclosure I know that every time i've fed my BP I use a hair dryer to dry his mouse off, and just from the residual airflow going into his tank, his temps kick up by like 10 degrees. If you have one, blow it around in there (make sure he has a full water bowl to keep humidity from bottoming out, but even if it drops for the few minutes you're heating up, it'll rectify afterwards)

not a perfect solution, but it works, and quickly, until you get his ambient temps up.