Online Lead Generation for a Sellers Marketplace

I have a marketplace website where users can sell their products for free. There are no listing fees and no commission on selling. The only fees we charge is when a user uses listing feature upgrades. A user can list his products, unlimited products for 365 days for no fee. I need a good online marketeer who can generate us active sellers. Active sellers are the ones who at least list one product to sell on a 180 day or above listing and accept online payment via paypal.

We would pay a lumpsum fee for such per 100 leads/active sellers.

Give us your price with a brief plan stating how you intend to achieve it.