I believe the front wheel from the Euro XT 660 R is the same or very similar to the WR. It might just bolt on if you can find one. The hub seems to have the same part number and the front disc is 298mm.
http://www.bike-parts-yam.com/yamaha-microfiches-affectation-piece.html?text_recherche2=5VK-25111-00-00
Not much chance of finding on of those here in Canada so I put on an aftermarket from wheel for a KTM 640 ADV. This is an easy fit and I was able to keep the stock WRX brake. More info in my post about it.