I have a back pack I took to Hawaii this past summer, it made it very easy to store things that I needed to get to quickly, as well as easy to keep up with things as we walked around sight seeing or going to the beach.
It is one I bought a few years ago to wear when I was riding my motorcyle, I will look up the name for you. It has plenty of room and multiple compartments, as well as a system that allows you to loosen the pack away from the straps on the neck so it conforms to you, more.
I love it, and have used it more off the bike than I did on the bike.
Good luck with your search.
I found it, check out this link, and then you can do more research from this
http://www.motodepot.com/product_detail.php?cid=910&sku=581
the helmet strap tucks away in the bottom of the pack