I just got mine at the local KTM dealer. The seal and O-ring are cheap. The bushing will run you around $20-$24. They're parts that most dealers should have in stock. When mine started leaking I picked up the seal and O-ring and changed them out but it still leaked. Had to go back and get the bushing a couple days later and once I swapped it out I was golden. You'll probably save a couple bucks if you order on line from some place like Munn or Cycle Hutt.
I've got a little over 6K on mine and it's been one of the best bikes I've ever owned!