He's not a big enough "name" (alas) to be able to snag a guest membership at this late a date.

WRT volunteering, most conventions out here ask you to pay for your membership in advance, which you then "work off" at $x/hr; you can either get a check cut at the end of the weekend or roll that over for a membership to the following year. (Which is why I'm not volunteering at Pantheacon that same weekend.)