I opted for a different kind of chemical toe warmer. I ditched the individual 7.4V battery packs for each boot and run both off a single higher voltage battery now. The controller with the "In Out" on it is the one I'm using for my boots, and the one above it is for my gloves. I mount it to the inside of my jacket with velcro and connect it to a USB-C battery with the cable on the right with a red end. Inside that red heat shrink is a little board with a USB-C connector that tells the battery to give it 9V instead of 5V. The controller didn't need 2 outputs as I ended up making a long Y cable to go to the bottom of my tights, then added cable guides inside the tights and a hole just above the top of my boots. With that change both my gloves and boots use the same kind of battery, so in a pinch I can switch them, plus I have a spare battery that can be used for either.
Its been unusually warm so far, so I've only used my boot heaters twice this year. I haven't even been bringing the battery with me lately.
