I really like propsavers, but the o-rings are unnecessarily expensive. So I made some DIY replacement rubber bands out of the inner tube of my bike tyre. My tube was flat anyway, so it didn’t cost me anything at all.
Notice that these rubber bands are a lot softer than o-rings, so they are best used for light propeller purposes. You might need to use more than one rubberband on the propsaver if you make them thin.
Here is a quick DIY guide on how I did.