Originally Posted by
JSnow789
I don't have one yet-otherwise I would.
eta: I supposed I could use a giant plastic yard waste bag...
If you want one - Bike Friday and Dahon both have a number of soft bags that would work. You could buy from either company and have the bag in short order.
You might also be able to use a large backpack rain cover from REI. Depending on your bike it might do the trick and be close at hand. But, ultimately an industrial sized garbage bag would also solve your problem and perhaps stop anyone from wanting to know what was inside...