These devices need a lot of current though. But perhaps you can carry a backpack with a large battery.
The boat 12VDC hair dryers/defrosters look promising. Batteries are no issue, I have a constant inflow of used 12V 7-12AH sealed lead acid batteries that aren't up to par for their intended purpose, but will work for this purpose.
Is this an informal test, or are you doing some sort of certification/safety test? For the latter you need to know what standard you are testing against in order to know how to test it, and your test equipment would need to be calibrated.
I know all about it.