Dave,
You should be able to go to an electrical wholesaler that stocks Belden and get them to order a roll in specially for U (if they don't stock it).
1585A has teflon coated Cu but with an overall PVC jacket. 1585LC has a teflon jacket ... obviously, if you're gonna strip off the jacket to braid/twist it, you don't need this but if you're going to use it in its jacket for long speaker runs, it's the one to go for. You may have to buy a 500' roll, though!
Regards,
Andy