I've had the same problem, too.  My local Ace Hardware store has a wide
selection of springs and I was able to find one that works.  They have a
board with all their springs attached to it, and a number by each one.  You
bring your old spring in and find one on the board that matchs, then look in
the drawer that has the same number as the spring on the display board.  This
is kind of an old-fashioned type hardware store; I don't know if the bigger
chain stores have springs like this or not.  Pat

Pat Walsh, '71 Westy, walshp@ippdsgi3.nawc-ad-indy.navy.mil