Most large companies have vendors. You can typically become a vendor via their supply chain management system. They usually have a web page where you can register your company, provide a list of services, and such. You also need to qualify by submitting liability insurance documents and such.

This is the best way to route around recruiters. It is hard work though. They usually have vendor fairs where you have a booth and give out brochures, advertise, network with internal managers...