I have a couple of vests that I like. Neither are of stretchy material. I could make a pattern from the vest I have by laying them out on newspaper and trace around the vest. I would probably lay the vest in a linear fashion on the newspaper, so that I could start with the center front and roll the vest around until I had drawn out the whole vest all the way without any side seams. You will still have shoulder seams but you could use binding seam on those to finish them on the inside. fyi,,,I am a little bit on the boxy side these days. I don't need darts or anything like that so this method would work for me. But if you want other choices:
https://craftingagreenworld.com/articles/vest-patterns/
I put this in my search engine and came up with a lot of great ideas. Lots of them free.
drawing a vest pattern from a vest you own on newspaper