From reading around it appears that he still does stuff publicly, but is very picky choosey, and prefers to avoid the over-commercialization of most conventions. You may have luck getting in touch with his agent. I don't have any of the pro accounts (like imdb-pro) to get access to dude's name and number, but with your vast audience of megachads, someone should. Have that person reach out for a quote.

I think the community could pick up the tab on that one.