In the past King Canvas out of Seattle has made many of the camper backs. I recommend that a local canvas worker make the canvas. The reason is that fitting to the boat is key. I have seen some remotely made canvas be inferior in fit and finish to what can be obtained locally. I have seen excellent camper backs by King Canvas, and I have seen some which I considered sub optimal. It is certainly possible that King Canvas has more than one level of finish--I don't know if that is it, or that there are more than one person doing the building of the camper back, some good, some not so good.
Do you already have a Bimini top? Do you have an awning rail on the top of the aft cabin? Is it aluminum or plastic? Do you want a zip out portion of the Bimini top to have easier boarding?