How to find comps in a sparse area

[David Simon]

I am looking to Brrrr a duplex in South Jersey. I've found a property that I like at what seems like a good price. But in order to make a Brrrr work, I want some comps to see what I think I can refinance at later. Otherwise, I'm just guessing when it comes to budgeting. But using realtor.com or trulia doesn't help, because they can't find any comps in the area that recently sold.

Is there another way to search for comps that I can do on my own? Or should I just expand my search our geographically until I find similar properties? I want to use a method that will approximate what a bank's appraiser will use, but I don't know what technique such a person would employ. Any suggestions would be greatly appreciated.