I made my own after purchasing a set of frames first. It was pretty easy to make and saved a bundle over a custom unit from a loft. I agree you should look at SBO or others, Biminis are pretty common items and you can buy them pre-made but if you want a custom fit to your boat with enclosures and such you'll need to find a good canvas shop.
They are easy to install, just two deck fittings so you have to drill four holes in your boat, all the rest can be done with fittings, tubing, and the stern pulpit. I've seen one set up that has the whole mount on the stern pulpit so no holes drilled in the boat at all.