We had our bimini replaced in 2019 by Don Gioia himself and I learned a lot about the history of who, what, when and where for the canvas and other soft goods on the Mainships, Silvertons, Hunters, Luhrs, etc.
Gioia made the OEM canvas and vinyl upholstery for most of those boats when the boats were made in NJ. When Mainship moved production to St. Augustine, another local shop replaced Gioia. But in the early 2000's, I believe, Gioia bought the St. Augustine shop and started production again, that is, until Mainship shut down.
The Florida shop, now owned by Gioia, did have the pattern for my 2004 MS400, but it was a paper pattern, not in good shape. Don came to my boat in Maryland and measured everything and made an excellent bimini with side curtains and also re-upholstered the helm seat. All top-notch work. He did it over the winter and knocked 10% off the price. They also installed it, however on my old Silverton, I bought the top and side curtains (they had the computer patterns) and installed it myself in about 1/2 hour.
All I had to do is put up the top and then install the "lift-a-dot" fasteners to mate up with the existing posts that were on the boat. A simple DIY job for anybody with basic skills and the ability to reach the spots.
Bottom line is there's a good chance Gioia made the original top and also a fair chance that they have the patterns someplace. I would contact them and ask for Don or Dawn at 732-901-6770.