You could keep one of these hand warmers on your desk and warm up occasionally, or stick a toe warmer to the back of your hand?? My mom uses them every day. I’m just spit-ballin’ here, people.
Costco sells a pretty good size box of the Little Hotties as does Amazon. You stick them in gloves for snow activities.
Well if this is something that is really important to you and you are willing to spend the cash I would say look into dew heaters for telescopes. They have multiple channels supporting multiple straps and are imminently adjustable from 0-100, and super high quality with heating elements spaced equally around the strap.
I want to say at some point I found fingerless gloves at Fleet Farm or a similar farm/work-supply store.