If I remember right, you guys already did something like this once, but there's always the automotive departments at walmart, sams, etc.
You could call people about their cars. Lots of times people are shopping in the store while they wait since it takes several hours, so you could call them while they are at the store even.
Again, I'm not sure what you would say to get the customer info.. Speaking of Sam's, maybe you could get the info for customers of members only stores like that. Say something like you're calling from corporate to verify some new member info or something
There are several stores around here like Lowes that ask for your phone number during check out. They say its just to keep a log of where their customer base is, but any time you're at a store like this you can eavesdrop and note the person's phone number. Then you can call them up and say you're from the store they gave it to