Great lakes boat tops might have been the original manufacturer for your boats canvas. If you are happy with the layout of your current canvas its worth checking out. Just google them and they will come up.
I just replaced my boats entire canvas (ie: bimini top, side curtain enclosures and aft curtain) for less than $1,000. The only catch is you have to install the snaps on the canvas since they don't know where the male snaps are on your boat.
It also came out very good.
--Steve