Print this one if you can https://www.youmagine.com/designs/alternative-um2-feeder-version-two
Its the most widely used and is very good. It also make it faster to change materials and easier to clean the knurled knob.
If you are unable to print it, then I'm sure someone near you could.
Not good that you are having these issues but as hal-9000 said. once you are passed them im sure you will love it.
I had a few issues to start with but I stuck with it and I'm really glad i did.