I am not sure if the HW diopters ever came with a rubber eye cup when new?
I have owned dozens of them over the years and some had rubber eye cups on them - but they were all different - and so I thought they were just added at random by previous owners that liked the idea of using them with a rubber cup fitted.
As they are a standard size (fitting wise) you can fit any type you like the look of.
Mine have had Anshultz, Walther and Feinwerkbau types fitted - along with some unbranded types of unknown origin - but I have never seen one with an HW badge moulded into it - but to be fair they were always pulled off straight away (if they were fitted) so not too much notice was ever taken of them.
If you really do want to fit a rubber eyecup I always thought that the Walther ones looked the neatest and were also the shortest - all the other makes were longer and come with bellows on them and never seemed to sit straight once they had been used for a while.
The only rifle I liked to have the bellows type eyecup on was the FWB 150, 300, 300S and 300 SU as they helped to protect the eye from the sledge sliding backwards when I was a little too close to the rear sight ( I think we have all been there - and it can hurt!).