Find a local boat canvas company and take them the old one. They should be able to make you up one. 1" stainless tubing holds up really well and should be the last frame you buy.
i have a gibson and just had a extra bimini made for the rear deck.105in wide by 10 feet long with 1 inch tubular frame and sunbrella canvas for 900$. i use a local car canvas and interior shop. i learned if the sign in front of the building doesnt say " marine" its a lot cheaper. just a idea for ya.
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1991 gibson 44 executive 454's norwich,ohio docked on the good ole ohio river in marietta