A clip for Curtain rail, snap into place and slideable. 

I've found the orignal clips snapping, and replacement parts seem way to expensive.
I've redrawn the orignal ones and made some changes. 

Printed in PETG.

Best way to print is sideways down ( or up ). So the clip is strongest in the direction it is used. 

File uploaded in Step format, so adjustments can be made personally an easily.