Yes, there are several Gnostic Christian churches. I belong to one of them.
The Ecclesia Gnostica has been i the US since the 1950s, and originated in England. There are parishes in Los Angeles, Seattle, Portland, Salt Lake City, one somewhere in Arizona, and a new one starting up in Houston. There’s also a parish in Norway. It’s probably the most traditional of modern Gnostic churches.
Closely related is the Eglise Gnostique, of which there are at least a couple of branches, and it descended from the French Gnostic movement. They have more of a presence on the eastern side of the US, and generally have a good relationship with the Ecclesia Gnostica although they’re separate traditions.
There is Ecclesia Gnostica Mysteriorum founded by Tau Rosamonde Miller. She was consecrated a bishop of the Ecclesia Gnostica in the early 80s, but broke away from the church and now has her own tradition with its own unique liturgy.
The Apostolic Johannite Church is also quite popular now, and it started in (roughly) 2002. They have parishes and groups all over the world. They claim to be based on a tradition of St. John, they have more of an occult leaning, and their apostolic succession is questionable. But I know some very nice Johannites, and they seem like good people.
There’s also the Alexandrian Gnostic Church, which I don’t know much about. They’re part of the North American College of Gnostic Bishops that was established by the Johannite church, and also incorporates Thelemic bishops.
There are several other Gnostic churches around, but at least in the US, the Ecclesia Gnostica and Eglise Gnostique are the oldest. Many groups, like Sylvia Brown’s, use the word “gnostic” but have nothing to do with ancient Gnosticism – they’re mainly just modern New Age groups that like to use the word “gnostic.”