I, too find it hard to find jewelry that actually fits. With a 19″ neck most pretty necklaces don’t come even close to fitting. Like you say, many websites don’t give sizes, but I go in assuming that bracelets are typically only about 7″ around, so aren’t about to fit me since my wrist is almost 9″ around.
That said, I’ve taken to trying to find things made for men that aren’t as obviously masculine. That can be difficult.
I’ve also started making some of my own jewelry. I’m not great at it, but at least I know it fits. There are lots of hobby shops with jewelry parts and pieces and it’s apparently a pretty common hobby. I know one person who even make a little side money making earrings and such.
And, fortunately for me, buying in person is possible, so sometimes I can try things on and see.