I was unable to find any replacements for the perished eye cups for my mum's old binoculars so ended up making some.
They worked out okay and while making them I realised that I could improve my rangefinder with one.
A great improvement, you can use it one handed now. Before it was a bit wobbly and really needed two hands to keep it steady to your eye. One handed I can now hold it on a 200 metre telephone pole reasonably well.
The rubber section I used is a sqeegee refill rubber from Screwfix, the round edge makes for comfort. I superglued it to an O ring which grips behind the standard eyepiece.
As far as I can see all the rangefinders of this configuration would be improved with one.
The only disadvantage found so far is the holster flap is now a bit tight!
Hope this helps someone else. If you find a better source of rubber extrusion please let me know.