I won a set of these Croakies ARC Articulating Reattachable Cable Retainers for your sunglasses and have to say that these are the best glasses retainers I have owned. The this cable keeps the retainer of the back of the neck and getting caught in you clothing. The system comes with a large and small set of temple plate connectors and snap in and out by the ball and socket joint. These go for around $11.50 but, well worth it. You would never know you have them on.

http://store.croakies.com/arcsystem.aspx