You either hire a canvas shop or get a kit from Sailrite.com and do it your self. Here's a list from a google search "marine canvas in Boston" I suggest contacting a few of them... most will have examples of their work online.... tell them about your boat and they can probably give you a ballpark estimate over the phone. Options you'll want to consider are: stainless frame with welded rear grab rail, premium glass, protective cover, etc.
I had one custom made by a local marine canvas guy ... $3100. well worth it, I think.
I had one custom made by a local marine canvas guy ... $3100. well worth it, I think.