When I bought the Ryobi One+ brushless line trimmer and expand-it blower I had a shoulder strap that I couldn't use, probably because the One+ line trimmer didn't come with a suitable place to clip on the strap.

3D Printing fixed that! This simple bracket was created using OnShape.

I printed this with PETG (because that's what I had loaded at the time) and 40% infill. No supports are required.

You have to remove the ratcheting clamp in order to slide this bracket over the shaft. Said ratcheting clamp uses a reverse threaded nut + torx bolt to retain the knob, and once undone it should come off with a little bit of prying and pulling. Use M4 bolts and preferably nylock nuts to clamp the bracket onto the shaft.