this would work too, and is actually stranded wire vs solid. BUT this will also be thicker and is a touch over $3 a foot, whereas the t-stat wire is ~$1 a foot.Just Froogle "10 conductor cable" with the quotes... Add "16 gauge" or "18 gauge" if you want. e.g. Portable Cord, SOOW, 16/10, Cut to Length - Electrical Wire and Cable - Wire and Cable - Electrical : Grainger Industrial Supply
Or you can just get some TechFlex and run speaker wires inside of it.