The Modified Zip Top Bag
This is similar to a Ziploc sandwich bag, but nearly indestructible and nearly the same weight.
You will need:
1 zip top bag (I prefer zip tops with a double seal)
1 roll of clear packaging tape
1 roll of duct tape
1 pair of scissors
Put rows of clear packaging tape over the front and back of a zip top bag. Make sure you don't get any little air bubbles under the tape. Then put a thin strip of duct tape over the seams and fold it over so the duct tape lays on both sides of the bag. These things are super heavy duty and with little added weight or cost, plus you can still see through the sides of the bags.