Mike I think you will have to go to a middle man with complete cats, most decent sized operations know the value of each cat and will buy whole, the refiners want very large regular amounts of un canned cats for their processes and pay close to market for the values from what I can gather.
How much material do you have?
In Europe at least all P.G.M's eventually lead to https://matthey.com
But you need to send in full drums of homogenised and milled honeycomb to take advantage of there system efficiently.