Anne Miller wrote: If so why not buy paper lunch bags?
I would think paper lunch bags would get pricey.
What do you plan on doing with poop after the fact? Garbage, compost, bury under a tree?
Consider what you don't mind carrying with you. Do you want to have to carry a bucket and trowel? Do you want to carry some sheets of newspaper to grab the poop with?
Do you take your dog for a walk with the intent that they poop then? My friend says they normally poop after a meal (my observations suggest it's not quite that simple...) Can you train your dog to only poop in one small area of your own backyard and that way, pooping on your walk will only be an occasional emergency thing?
I think that as Anne suggested, we need more information...