Last week I heard an interview with a classical guitarist who spoke of another prominent player who just plain had small brittle nails that would break, and they use nylon strings. But what he would do was use pieces of a ping pong ball. You can cut them fairly easily to size and they're cheap. However he actually made replacement nails that he glued on top. If you didn't want to glue, you might be able to create something like a ring. I think I might look into it myself, as I hate growing out my nails, but miss the tone.