For business, you have to hit up IMCs. Intermodal Marketing Companies. Ch Robinson, Mark 7 and etc. For international, NVOCC and freight forwarders.
Warning, there are a lot of Truck Brokerage doing intermodal drayage. Brokering out the drayage. A broker's bond does not cover intermodal, anything that touches the water or rail. You cant file on their bond.