Are you looking for a Bumper the rubber piece on the bottom of the cue, or are you looking for the part that the rubber bumper pushes into.
If you are looking for the part that the rubber bumper pushes into you need to send the cue to a cue maker to have it repaired. I would recommend sending back to Samsara not one can do the repair better than they can, and it is always best to send a cue that needs repair back to the original maker.