Orion's heated belt

We're away to Yorkshire next week and then on the Northumberland (Bellingham) for an astronomy themed meet up with the owner's group for our motorhome.  I've been doing a little research on astro photography and decided a heater to avoid the lenses fogging up might be a good idea. 
This one gets good reviews so I decided to give it a go.
Powered from a USB battery pack, I should be able to let it heat up on the motorhome supply before venturing out.  

Alternatively - yet another gadget to find room for - and a cable for tripping over too :-)

Gill has been at a crafts/sewing exhibition at the NEC today .... expect a few pyrography related arts blips at some point.