I think I can safely say greater DC area?
Washington, DC? That is an ideal place to be for your search, because of the Catholic University of America and the presence of many Religious student houses nearby. As for a list
Augustinians [OSA]:
Seculars & Friends — The Augustinians
Benedictines:
www.osb.org [Each monastery has its own oblates, which are equivalent to tertiaries.There is a monastery of the English Benedictine Congregation near Catholic University; its name is St. Anselm:
http://www.stanselms.org/oblates.php ]
Both branches of the Carmelites have a third order:
www.carmelnet.org for the Carmelites of Ancient Observance &
www.ocdswashprov.org for Carmelites of the Teresian Reform [the Discalced Carmelites]. Both observances have houses near the campus of Catholic University
Dominicans have a Pontifical Faculty near Catholic University, so they should be able to help you find the Third Order activities in the region:
http://laydominicans.org/ or
www.3op.org
Franciscans:
www.nafra-sfo.org The Franciscan Friars have a monastery, near Catholic University, and someone there should be able to assist you
Marists:
www.maristlaity.org – have a house near Catholic University; they would be able to give information about the Marist Laity/Third Order of Mary
Mercedarians:
http://orderofmercy.org/assets/3rd-order-pamphlet-scanned-10292014.pdf – are in New York
Minims:
conventi The Minims have one friary in the United States. It is in Los Angeles
Norbertines:
www.premontre.org There are four abbeys in the United States: De Pere, Wisconsin; Paoli, Pennsylvania; Santa Fe, New Mexico; Orange County, California. One of the European Canons mentioned to me not long ago that they have started a Third Order chapter in the Diocese of Arlington. I tried to look it up a moment ago and it seems to be true
http://www.stveronica.net/prayer-and-fellowship/norbertine-third-order/
Servites:
http://www.servite.org/about/servite-secular-order.aspx – The Servants of Mary have tertiaries but they are, to my understanding, based in Chicago in Illinois and Portland in Oregon where the Servite major houses are located
Trinitarians:
http://www.trinitarians.org/about/laity.html They have a third order presence in the Archdiocese of Baltimore
The Secular Augustinian Recollects should be attached to this province of Augustinian Recollects.
http://www.augustinianrecollects.us/
St. Teresa of Calcutta established the Lay Missionaries of Charity
Lay Missionaries of Charity (LMC)-
As far as contacts beyond Internet, you can call the chancery of your [Arch]diocese and those other dioceses contiguous to you and they would each have a list of the third orders active in their respective diocese
Also, any house of the various Orders that are listed above, and which could be contacted via the website, would be able to help you find a presence, if there is one, near you and also give you information as far as the local contact information.
I hope this is helpful.