We use ones from Rukka. Not sure if they’re available everywhere but they are they best ones we have tried (others always fell off, especially in deep snow). I think having two Velcro closures on each sock has been key. I also prefer the soft shell ones as our B seems to accept them more and they don’t twist as much as the ones with a hard sole.
Here are the ones I am referring to: https://rukkapets.com/paw-wear/thermal-shoes-black