Go to Cabela's and buy the biggest fanny pack you can buy in the hunting section. I've had the same one for 10 years now.

About the only thing I can't put in it (on top of everything else) is a rain jacket. If I think it might rain, I'll put on the old vest and put my jacket in the back pouch.

I do like the look of those sling packs but wonder about the effect on my back (which sucks as well). Also, is there a place for a water bottle?