For only a few bucks you can find a pair of really cheap readers at a drug store or dollar store and try them out. (I found a pair for $3 recently.) They come in a lot of different magnification strengths so you may want to try a couple of different ones. Different ones are better at different focal lengths, and the best strength for reading distances may not be what you prefer for closer work like tying flies or tying flies to tippets. Carrying readers around isn't as convenient as a clip-on for your hat, but you can use the cheap ones to find the best strength for your particular need before buying something more convenient like a clip-on or bifocal sunglasses. (And you can always hang them around your neck like a librarian when you don't need them.)
Once you find a strength you like, yes, you can get non-prescription sunglasses with bifocal magnifiers. I got mine at Bass Pro for about 20 bucks. They are good for reading at the beach, too.