You have a few options. You can buy a universal fit bimini like Dr Honda did or you can buy the one designed to fit your boat. The OEM bimini for yours runs 440 + shipping. The universal fit kind can be found on ebay for under 200. I went with the universal fit one originally just like Dr Honda has.. It looked good and functioned fine. The only problem is that it didnt really hug the contour of the boat when folded down and would not fit under the boat cover. I only tow the boat covered, so that was a problem. After I had a brain fart and bent it all up, i decided to buy the OEM bimini. It is a bit nicer and easily fits under the cover, bit is also cost more than double the price.
Either way, I highly recommend it. I use it more for rain than I do sun protection. Properly installed with the rear poles it can be in the folded back position and not effect speed at all. With it open i can do 35+ easily, never really tried top speed with it open.