Windows 8 Full Version?

Hey guys, I currently have Parallels 7 with Customer Preview Windows 8 on my Mac mini. I would like to eventually upgrade to Parallels 8 (which is ridiculously priced and maddening that they wont properly update 7 to allow compatibility sorry for the rant)

Right now, I can find many resources on how to upgrade your older version of windows to 8 but it is almost impossible to find the full version. I have multiple XP discs on now thrown out PCs, but no disc drive in my Mac. I dont want to buy a superdrive just for this purpose.

Can someone help me figure out a way to buy the full version of Windows 8 once I have bought Parallels 8? Thanks, this is driving me CRAZY