I always had problems with my son's banana/umbrella stroller getting dirty in the trunk of my car or the back of our truck. I noticed one day that we had a few folding lawn chairs that come in their own storage/carry bags. I got the biggest bag from one of our chairs (that had a footrest attached) and slid the closed stroller in it. All but the front wheels and the handle fit inside. I could also pull the drawstring to tighten around the stroller.
That is great...I have a blue gift bag from Walmart.com that may work for that!