/me starts hunting for another forbidden USB ASIC you cannot buy - Norelsys NS1021. This chip can transparently convert the USB 2.0 electrical signals to a true AC-balanced form for transmission over CAT-6 or coax cable, with capacitor or transformer isolation.
Not sure if I can use it. There's nothing you can't get from Shenzhen with enough persistence, but getting a leaked datasheet is more difficult...