I have a sit on top kayak that does not have handles. Is there a handle that can be added when there is no access to the back?
If you can’t access the inside to put a nut, not likely a handle would work. Rivets or threaded screws don’t usually get enough grip to hold the weight of the boat when you pick up by the handle.
One boat I added a handle to that didn’t have access to I added the access first. There was a spot in the boat for a hatch (flat round area), so I added the hatch (one of these: https://sealectdesigns.com/groups/3444-screw-out-deck-plate) and used that access to get to the inside where I needed the handle.