Nut used to secure hatch and other parts in the hull/deck

[Martha Pekelharing]

Dear all,
Hope you are doing well and enjoying sailing or preparations for summer!
I am writing from the Netherlands with a question about our CC19 Hawkins hull no 4

We are looking for a nut that is used to secure the hatch. One nut is missing, causing leakage.
I have approached many stores, but so far none of them know where to order it. I have also written to Honnor Marine, Tim advised me to order it from Lewmar, but also at Lewmar they are struggling to find this part.

I am not sure about the name of this part in English.. it is used to secure the hatch, but also other things on the deck, on the inside of the hull.
attached some pictures.
If anyone knows where to order this part, many thanks !!
regards Judith