I haven't got them with me ATM so don't know what brand they are but I picked up these floating straps at a boating store Whitworths, they might not look that flash by they work well.
They have a little toggle that you can pull up tight when you go out on the water, I originally bought the strap so I could wear my normal sunnies when just going for a flatwater paddle on my SUP without fear of losing them but I now use them for kiting as well.
I find my normal sunnies fog up less than all of the watersport specific sunnies that are closer fitting with rubber or foam around them, they feel fairly secure and although I haven't had them come off yet I think they would float and I would find them if I did.