I got these grips for my farm bike. They were under $15 AUD including delivery. At first I was very disapointed with them, as they would barely get warm running through the standard 1.5 amp cigarette lighter USB adaptor that I use on my bike.
After a bit of stuffing around with higher amp USB adapters, I eventually gave up and spent another $10 on a 5 amp 12V to USB converter that I connected directly to my motorbike battery with an inline on/off switch.
Running from the new converter, the IZTOSS heated grips now pull 3.0-3.5 amps, and get warm enough to make a significant difference on those mornings when the temperature gets close to freezing (which it often does where I am).
TheIZTOSS heated grips obviously aren’t as good as Oxfords, but even including the 12V converter, it only cost me $25 all up. Unlike the Oxfords, the IZTOSS heated grips is that I can remove them in around 30 seconds when the weather gets warmer, or even move them onto my road bike or ATV.
I’m not sure how long they’ll last, as the wiring could get caught on something and pull out reasonably easily – but if it does, I’ll just resolder it. So far they’ve lasted half of winter on the farm and in the bush, and haven’t fallen apart yet. At under $15 it would almost be worth buying another pair to keep as a spare.