Ask HN: Selling your contract work

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.