A couple of years ago I found relatively inexpensive and heavy-duty leak proof zip lock bags at a Web site called http://www.thewaterproofstore.com/.
I bought a multi-pack selection of four Aloksak bags (direct link: http://www.thewaterproofstore.com/aloksakmulti.html) for under $12, the largest of which is 12" x 12". The store has quite a few other nice products as well. I have no connection with the company.
The image below shows my old Panasonic ultrazoom camera, a small Canon not-waterproof point and shoot camera, and my old and still-in-use cell phone. The fourth bag in the kit has gone missing *LOL*.
I bought a few more multi-packs last December. They make great gifts for your fishing buddies, or perhaps stocking stuffers for outdoorsmen/women in your family.