T56,
  Is it one of the sockets with the universal built in or just a normal socket?  I know you state 3/8" drive, but what size? 
I give all the piles of sockets at my local swap meets a quick perusal and I find the occasional Plomb socket for my own personal collection, but I can dig a little harder for you this weekend.  It is the proverbial needle in the haystack though...
  Jim