A similar question has been ASKED
Here are the Locations
Route 3 (With Dowsing Machine), Route 13, Route 16, Pinwheel Forest (With Dowsing Machine), Desert Resort (With Dowsing Machine), Nimbasa City, Mistralton Cave, Chargestone Cave, Twist Mountain (With Dowsing Machine), Icirrus City (Winter Only), Anville Town, Victory Road, Abundant Shrine, Lostlorn Forest, N's Castle , Castelia City Royal Unova Gift.
Source
I love Weird things ¯(°_o)/¯
