Hi Emile,
Sorry to hear your problem.
This step was made specially for Hymer by Omnistor and carries a special code number of it’s own. They did that probably because of the dimension problems you are discovering.
I think you would be best off ordering one from Hymer, or at least from these people – https://tinyurl.com/qtt469f – irrespective of the expense, because I believe you may have far more problems trying to make something else fit (not that that is impossible).
I cannot suggest anything else other than just looking critically at dimensions of other steps, but I’m guessing that if Hymer had to have one specially made, it was for a VERY good reason!
Good luck with this, and let us know how you get on. Another step option, should you discover one, would be a very great help to others.
Best wishes,
Barry
