Previously I mentioned how cold it has gotten in our metal-framed workshop.
Well a couple of christmases ago I bought my dad an electric body warmer jacket for when he was out in the garden. I'd bought my wife a similar jacket for when walking the dog in -40c Calgary temperatures and she loved it.
He passed away right after so I asked my mum if he still had it.
It turned out he had, and never had it switched on! They didn't want to upset us so told us it didn't come with the power pack that should have been included.
I now have it and I am plugged into USB at my desk.
Yes, that means I keep forgetting and walking away while still tethered, but while connected it gives me a nice little heat boost around my back.
Excuse the dust in the picture, I had just been scrambling around collecting as much polystyrene as I could to put up against the metal sheet walls in an attempt to mitigate the heat loss. I don't think we have enough ;)
Doesn't look like my specific item is still for sale on Amazon but they have a large collection with some quite heavily discounted considering the weather.
Mine is a generic chinese brand anyway so just check the reviews and make sure yours comes with a rechargable battery.
Not just any battery will give the juice or duration you are looking for, it needs to be the kind that would power a phone fast charge or better.
This body warmer solution doesn't help the machines warm up so I ordered a radiant heat infrared heater, and if that works and is not super expensive to run we might buy more.
I am also looking at actual insulation as far as possible. Right now I am looking at XPS foam for ease of installation, cost, efficiency per square inch, and also it is not permanent, so I shouldn't have to get landlord permission.
Keep the suggestions coming, especially ideas that don't cost a lot!