A few CAT 8 cables are on the market now. Cables & Kits has a relatively inexpensive one and looks good quality. I am using one now, on my computer.
DH Labs makes a CAT 8 with better connectors and silver plated high purity copper wire for a little more money.
DH Labs makes a CAT 8 with better connectors and silver plated high purity copper wire for a little more money.