I designed this part to replace the broken quick release clamp. The diameter of the big tube is 32mm and the smaller (that goes into the big one) 29mm. Design is available in [Onshape](https://cad.onshape.com/documents/1044453bff2a17b881d43b5f/w/1b1904d9aa72818e4a208d1c/e/1a46a3bab9b3a0a7964ae307) if you want to modify dimensions according to your umbrella's poll and your printer's tolerances.