Sanding tools work best if the sandpaper is padded underneath. That allows it to better follow contours and overcome bumps. The easiest to source foam padding is foam double sided tape, which also solves the problem of how to attach the sandpaper.
These are very simple yet effective sanding sticks designed around standard sandpaper sheet size of 230 x 280 mm or 9 by 11 inches and uses strips cut along its length. The foam double sided tape is consumable with the sandpaper, by the end it's usually too compacted anyway, sticks are reusable.
You can get double sided tapes in myriad of widths. What you buy will dictate how wide you need to print the sticks. You can also tape them next to each other as double wide etc.
The models are 25mm wide, which is common size, but your sticks don't have to be. Put them on a side and set Z height to desired value (your tape width). Do not scale the other 2 axes or the circumference will be wrong.
Cut the sandpaper stripes with a hobby blade and a ruler along the length of the sandpaper sheet like on the photo. Same width as your sticks or tape.
Leave a 5 mm gap between the ends of the double sided tape. When you wrap the sandpaper, the ends will both end in the gap and the edge of the sandpaper strip won't strike the sanded object. That way you can happily sand even with the joint.

You can find the source files here if you want to edit them yourself. Just keep the circumference ~271mm.
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Saw handle for blades with 20x1mm cross section
The author marked this model as their own original creation.