threaded brass circle on my 1927 tank

[pete kneedler]

Dear Friends:  I am restoring a 1927 Austin 7 (the one with the gas tank behind the dash).   I need the threaded brass circle that fits on the top of the gas tank spout.  I did order a new gas cap from David Claiborne but it won't fit on the tank because of distoration and general abuse of the threaded brass ring on the top of the gas tank spout.  

Cant this threaded brass ring be purchased somewhere in the United Kingdom?  The specialists here are stumped by the thread pattern and think it might be of British pipe origin.  Help!  Pete Kneedler