After spending several hours trying the AFK method in Elder's Recess, and quick traveling between camps in Rotten Vale, I finally found one in area 15 of the Vale. What worked for me was checking both Mosswine in Rotten Vale on an Expedition, leaving and repeating. Found it on my third go with this method.

I got mine from Rotten Vale because it got stuck on the wall. I didnt even know of its existence, so I thought "The hell is that noise?" and saw this ball of fur (or more like feathers) spazzing out.