Handle. Created for a surfski Paddle shaft grip.

Select the file with the number in mm closest to the width of your closed fist excluding your thumb,
I tried the customiser but it failed: my model only compiles in wire frame mode in openscad. I've put up some different sizes for people instead. Compared to my fingers a lot of guys have troll fingers.
As compiled, fits a 28.52mm diameter shaft.
Print with a 1mm brim. Best one at a time, I tried a batch and got missed steps, it's a fairly straight forward print on it's own though.
You'll probably want to put some tape around it too (on the paddle) to be absolutely sure it doesn't slip.

For anyone who's paddled sea kayaks, multisport kayaks or surfskis, you'll know that wing paddles need fairly precise control of blade angle. There are high density neoprene? foam grips you can buy and also tape-on strips you can buy to make the paddle shaft eccentric but as an inventor, I've not been happy with any of the current options. Most people fit some sort of grip on the right hand side only and go with a 90 degree paddle twist between ends, I use something closer to 40 degrees difference which allows me to lock both hands to the paddle shaft.
Note that with a typical adjustable paddle, for the right side (Orka) the grip (if printed in PLA) won't fit past the adjuster and collar without breaking. Warm it with a paint stripping air gun on the low setting, slip it past the adjusting collar and then heat again and squeeze closed around the shaft again. If you are using ABS or nylon it should open far enough without these precautions.