I'm just curious if there is any service out there that allows you to buy and sell the current contract jobs you have to others in the form of leads / introductions?

When I need to part ways with a contract I don't want to leave the client without a developer. I've noticed that my recommendations are highly regarded by the client. Usually I will tap into my network and pass along the work no strings attached, but couldn't almost guaranteed work for a set amount generate revenue? I'm sure there is something out there and would like to see it.