have you tried Hippo Hands https://www.hippohands.com/
Way back in 2006 or 2007 (I think it was the latter) I did try Hippo Hands on my 2005 Burgman 650. I had just come off from riding a Gold Wing and the coldest temps I rode in with the GW were in the low 20sF. The biggest weather protection difference I noted between those two was that on the Burgman my hands were out in the wind and on the GW they were not. So on the Burgman my hands were feeling the cold breeze a lot more and I knew I had to do something.
I knew from many many years before that how those were the best to be found for handlebar muffs. That's what Hippo Hands are... one brand of many handlebar muffs.
Anyway, the very first day I tried those was on my morning commute to work, about 6:30 am, and the temp was the coldest I had been in while riding up to then at -5F. My hands were still frozen. Turns out the only set of HH I could find were the "newer style" that had a lot of open seams and the air just streamed through them like they were mesh. That ride convinced me to go with the heated gloves and the HH were immediately returned.
Now I am finding there are a great many options for handlebar muffs or mitts to be had. Back then there was only the HH and one or two others to be found. Now there seem to be many dozens, some of the same ones sold with different "brand names" applied to them from different sources. The Hippo Hands of today look to be a LOT better than what I had used 15 years ago, but they also cost a LOT more. Just a few days ago I decided on a set of handlebar mitts that cost 1/5 what the typical HH costs so will see how those work out. If they don't do the trick I'll more likely stick with my heated gloves since those have kept my hands warm down below -15F with no issues.
Of course using my heated gloves means installing the harness more permanently than it is now installed. Something I am hoping I don't really have to do. So far the only issue I've found having both the heated gloves and heated grips turned on is that the grip heat sensor seems to detect more heat than allowed, thanks to the gloves contributing, and they issue a fault indication and turn off. So if the handlebar muffs don't work out to my satisfaction and I end up sticking with using my heated gloves for those temps below around 20-25F then I'll simply not turn on the heated grips while the glove heat is turned on. Hands are warm either way. Grip heat only down to about 20-25F and then glove heat only below that.
To be honest the only reason I want to try the handlebar muffs is that they are a passive solution that I hope will work to keep my hands warm with the integrated grip heat already on the AK so no need to install something else electrical to do that job. Adding electrical stuff to my bikes is easy for me. Very closely related to what my career was before I retired. But I don't like to modify what the factory provided any more than I have to. Things work better that way.
