How Best to Monetize Barter Spots?

I represent a small start-up that provides imaging and other services to news/talk and sports stations. The company is looking for a way to sell the barter spots they receive from several of their clients. (Odd, I know -- they started accepting barter before they had a deal to sell the spots.)

Any thoughts on how to monetize this inventory? It's currently a small number of spots from just three stations. Too small to work with a Dial Global, et cetera. But, if we get a sales system in place, several more stations are ready to sign on as barter clients.

What about hiring an independent seller and paying a hefty commission?
If you'd like more details, please email me at randall.bloomquist@gmail.com