equifit curb chain cover works well
Equifit and acavallo have nice high end options. Other options, that are cheaper, are to latex, vet rap, or electrical tape it. Leather tends to rub a bit more and it's harder to find leather curb chains.
Equifit makes a curb chain cover
I've seen a lot of people wrap them in vet flex or latex.
Put a gel sleeve on the curb chain.
Acavallo have it and they are very good!
use a leather curb instead of a chain curb