Blinds Spinner Holder

At our church, the blinds spinner holders/wallmounts broke (because of a very poor design). I found another holder (see Sources), but when I downloaded it, it didn't look correct so I designed my own. I've printed 4 but I forgot to take a pictures :-(

The holder is designed for a spinner with a diameter of around 15mm.

The photo is of a prototype I printed. I've also included a photo of the original holders.