When you say "find sails" that sounds like you are looking for used sails. Personally I would say not to do that, used sails often are so far blown out of shape that you will be cheating yourself, like buying gasoline with water in it. Any loft should be able to look up the stock dimensions and patterns for your sails and any good one will also tell you to take measurements because rigging isn't always original on the boat.
The dimensions don't have to be exact, but any time you change the dimensions you will change the performance and balance of the boat, sometimes for better, sometimes for worse, sometimes so little you can't tell.
And yes, sometimes you luck out with used sails but then other times, you don't like them and what you lose in shipping them both ways could have been used to just buy new sails that work and fit right in the first place.
Like Clint Eastwood said, "Do you feel lucky, huh? Huh? Do you?"