Tweets:
Based on offline inquiries, I repost with more info:
Brand names (not an inclusive list, but these are in my possession at the moment)

HEAT FACTORY
HOTHANDS
LITTLE HOTTIES

I take no responsibility for nomenclature..

locations
REI
BIMART (Oregon)
COSTCO (via my neighbors information)

They have also been seen at checkout stand of pharmacies, and are available in quantity by the boxful at the 3 above locations.

Happy hummer observing
poppe