USN is part of a package. If you're a DirecTV customer try calling them and seeing about adding it. They often do 'specials' where you could get that package very cheaply for the first few months, and can drop it afterwards, IIRC.

USN is only standard definition though, which (to me) really suffers by comparison to HD. And from watching some of the Vuelta last year, the actual TV work is not up to the standards of the Tour: fewer cameras, etc. It's certainly shot HD though, so it could be broadcast that way, it just isn't.