I took a small rubber wheel with a hole in the center, trimmed off a small round slice and slipped that over the bar between the lever and housing. To hold it in place and apply a little pressure against the lever, I used a black zip tie. Provides perfect friction to hold the lever and easy to make.
After taking the pic and looking at it, it would have been much easier to use an o-ring, cut it and squish it in there and hold it in place with a zippy or even a rubber band. If you wanted, you could try stretching the o-ring over the assbly but it would also be over the wires and cables on the bottom. A person could probably use a rubber band doubled over a few times and get the same result.