You can find such a group at just about any divinity school or theological school campus! The Society of Biblical Literature (SBL) is a group students, professors, and other theologians whose mission is to "foster biblical scholarship." Membership is open. Each year the SBL holds a convention at which members present papers for discussion and debate. Elaine Pagels, author of "The Gnostic Gospels," is an SBL member and has written several monographs for the society's publishing arm.
Another society that may be closer to what you're looking for is the Gnostic Society. On its web page, the group states that it is "dedicated to advancing the study, understanding, and individual experience of Gnosis." This group offers free online lectures and provides links to various gnostic societies around the country. This group also maintains a searchable online library.
Visit the links below for more information.