I was wondering what was used to generate the the patten in the gelcoat when the deck / cockpit areas were cast and more importantly is it available in some sort of fashion so a new area of glass work can have a similar non-slip pattern to the rest of the boats deck areas.
Aside from taking a mould directly from the existing deck areas and then casting up new glass work onto the mould which seems like a huge job...... a simpler way must be available
Now you are rather stretching my memory as that was over 40 years ago.
I do remember buying a roll of "Nautolex" non skid flooring material from I think it was Clark Rubber,and later seeing it in a local marine chandlers , so I would suggest you take a photograph of your deck pattern and try the chandlers first and see if they can match it.
Be sure to use some mould release on the fabric before laying up.