Kinectimals

You need to play a 2nd playthough as a 2nd profile until you reach the 2nd activity of the 2nd area (fiddlers beach). You must actually complete this activity then collars should be avalible at the shop. Sign in as your primary profile (the one that needs the achievement) then travel to the shop and purchase any collar or pendant.

When I got this I didn't even go to several of the activities, i only completed the 1st activity in the 1st area and the 1st and 2nd activities in the 2nd area, which makes me believe you only have to finish the 2nd activity in the 2nd area to unlock the ability to buy collars.