We found these inner cables from one of our suppliers. They feature a "31-Strand" construction meaning lower friction, extra smooth performance and better durability.

Specifications
Branded "Alligator Superior Shine 31-Strand"
Special high-tech treatment, non-coated ultra smooth surface
Durable, 3 times longer life than 19-strand inner cables
Eco-friendly and non-toxic
Slick / Stainless Steel

Mfr Claimed Weight
TBC

Note: Sold as a single inner cable.