I bought a sealed dualshock 3 and it's genuine (tested with MGS HD collection) so I figured maybe it can help you as a reference when looking for original ones online :
Dualshock 3 Deep Red Original Controller (Brand New and Sealed) Ds3 for PS3, Video Gaming, Gaming Accessories, Controllers on Carousell
How to Connect PS3 Controller (Original/Fake) or Dualshock 4 to your PC | Kunmi's Space
Sony Dualshock 3 Wireless Controller for Ps3 Black