Motul, Motorex, Putoline. They all have fully synthetic 15W50 or 5W50. Any one of them is a good choice. I used Motul 15W50 on every bike I owned, so far it is a great oil from what I can tell.
Just called the local KTM/Husaberg dealership about oil yesterday. They're pretty competent - they use / recommend / sell Motul 7100 and 5200. 7100 for my 570 they said. (I'm going to use 300V actually, but.)