I use these
Shimano M020 mountain shoes. But, they are out of production.
So, you need something that is for casual cycling, but you can easily walk in. If I were in the market for shoes right now, I would probably go with these
Shimano MT33s. As is frequently the case, Nashbar has them on sale for 20% off.
As mentioned above, using walking shoes for cycling is not a good idea. You'll find the arches and balls of your feet will get achy and tired.