I think the best place to find renters or sellers for lease options is on Craig’s List. You need to advertise on Craig’s List and state specifically what you are looking for; for example, if you are looking for a renter to buy a home, then advertise in the renting section of Craig’s List. If you are looking for a seller to lease his home, then advertise in the “For Sale” section of Craig’s List. Also you can find sellers on Zillow and Trulia by calling the “For Sale by Owner” home owners.
I’ve heard of investors doing bandit signs to find lease option tenants. Haven’t tried it myself, but with enough consistency, something like bandit signs usually drums up some progress for what you’re looking for.