+1. And I like to add for bringing your bike inside stores does not mean that it is necessary to have it completely bagged all over the bike-just cover the top and the sides from prying, critical bike hater's eyes. That means that simply using a light cover made of the above fabrics or similar fabrics not listed just like Dahon once did and Brompton still offers in it's slipcovers:

http://us.dahon.com/accessories/2010/carryon-cover

http://www.brompton.co.uk/explorer/accessories/index.asp?bp=14#
(The Brompton's cover would not fit Dahons, but the idea does work nicely on all my bikes as an present owner of a Brompton & a Raleigh Twenty, and former owner of 2 (one 20" & one 16") Dahons will testify to-the photographs below is the Brompton's version similar to my own. These bags are sold through www.foldabikes.com-the original US Brompton dealer).

I have several "homemade" slipcovers for all my present and past folding bikes. All were sewn on household domestic sewing machines. You don't necessary need to use a industrial sewing machine (although they are nice to have) or too heavy of fabric (bottoms-weight is fine) to have a nice durable cover of any style.