If you like the cables you already have, go the eBay or Amazon and search for braided nylon sleeving. There are some white ones there. It will cost very little. Then just finish them off with heat shrink tubing to fasten the ends.
Go to any YouTube for DIY speaker cables and you can see how it's done.
GR-Research's website also sells a white DIY speaker cable kit that is high quality and great value for the money..