My 15 year old blinds started falling. Found out it was the roller part that does the tilting. So figured before i started replacing all of them it could not hurt to try to model a replacement part for fun. Well, it works grate and now for a few cents instead of hundreds of dollars, I know have working blinds again.
This is for the 2" blinds that used the twist pole to tilt the blinds.

Printed in PETG, 0.2mm layers, 4 walls, 3 top/bottoms, 20% cubic infill.

The rod they slip on is a 4mm square bar. The hole is exactly 4mm square. For my printer it was very tight fit, but slightly heating the tip of the rod allowed them to slip on easier. Then string will push in the 2 holes on the top with the metal clips still attached. I use needle nosed pliers to just them through.