Tim, Your boom (and mast) appear to be identical to mine and were made by Le Fiell Spars, 800.451.5971 but sadly, they closed shop at the beginning of this summer. I spoke with them a month or so after that inquiring for parts for another E31 owner and was told by the chap that he and other staff had no idea what inventory remained and that the old timer had recently retired. It was all gathered into a pile in the back of the warehouse awaiting the junk man. You might want to try looking for one that will fit your track by calling around the country through the Good Old Boat Magazine list here:
http://www.goodoldboat.com/resources_for_sailors/consignment_stores.php I can't tell you how helpful that list has been to me over the years when I was ready to give up looking for some obscure part. Go for it, Glyn
