A local agent can set up a search for you in the MLS. However, very few properties get listed that way. You need an agent who will do some digging for you and call other listing agents to see if their owners would consider a lease with option.
Two things: be sure you know the difference between a lease with option and a lease purchase and 2. In a buyers' market where prices are on the decline, I don't think a lease option/purchase is a good deal. You will have to come to an agreement on the price today, but don't know what the value will be when your lease is up and you need to proceed with your option or worse, your purchase.