Generally there is no reasonably price for what you want. A used one is that and unless in pristine condition, not worth customizing the boat (snaps, moving handholds, latches, pipe stands, etc) for what may be an ill fitting or problematic comfort. And canvas/clear that may only last another year or two. I really try not to put more holes in the boat than are needed.
I have found that a good enclosure is one of the necessities on my boat. It allows more living space when the weather is iffy, protects me from weather while sailing and more.
Your best bet is to ask around your marina, or a boat owner who has an enclosure that you like the looks of - who did theirs and would they use them again. Be careful, as some enclosures ruin the looks and function of the boat, yet others look like the boat was designed for that enclosure.
A good one will cost some $$, so be sure to ask the maker how best to care for both the fabric and the clear. Some last longer rolled and most clears require a specific cleaner or liners to keep them in great shape. Just a few years back the connector ( 3' of bordered clear, between the dodger and the bimini) for my 42 was over $500 but it was so well done, it zipped in place where the old one was, like it came with the boat.