RSVP Plugin and Guest Unique Codes

I’m quickly looking for an RSVP plugin or some kind of utility (and RSVP Plugin seems to be the best one that currently exists for WP) that will allow me to issue invites to an event to a predetermined list of guests (while allowing new guests to invite themselves).

I’m specifically looking for a plugin that allows users to input a code or identifier (like an email address) unique to each attendee, that they can input which will allow them to pull up their details (like first/last name, etc).

Does anyone know of a plugin like this that exists?

Thanks