This should be a really tight fit. It does take some effort to push it on. If you don't have the same exact model there's not much I can do as I took the measurements off the Elna Pro DC 5. If you have some calipers to measure the part on your machine I can see about modifying it. In the meantime I have uploaded the original OpenScad model to Thingiverse. If you bring your Elna and the OpenScad file to someone at the library who knows OpenScad they should be able to modify it with a larger hole with minimal effort. The line that creates the hole is:
This was meant to be a very tight fit - printing it loose does not work well as there is not metal spring clip to hold it on.