I went to the army surplus store and got a fishing type chair with a toilet seat (sort of) on it for $11.99 and a Wag bag. We tried it out, not really, and it works fine. The Wag bags are the best and easiest in my opinion before and after use.
Once used you can use a big Ziploc bag and keep them in there. As far as storing that bag???? I am planning on installing a 6-8" wide tube about 20-28"s long under my truck with caps on the end, no smell, no leaks and all is well.