I added a set of Wald folding baskets to my rear rack on my 'grocery getter' bicycle. They fold up very nicely, are adjustable to avoid heel conflicts, and are well made. Just add a couple of the newly popular reusable grocery bags and that adds the portability you need to go in the store.

Just another option, maybe worth a look.

http://waldsports.qbsoft.com/index.c...ingbasket.html

Mark