I believe you can be a member of Beta Sigma Phi and be a member (or ex-member) of an NPC sorority. If you can, something like that would work. It does have a long and significant history and is not tied directly to collegiate life although I think they might have a few collegiate chapters. And of course that's not the only sorority of this type; it's just the only one I have ever had any personal interaction with. They call themselves a non-academic sorority, at least per Wikipedia which we all know is 100% right 100% of the time.
