A lot of owners use the J2 style wing stays, I am not sure as to availability but our main suppliers should be able to help?
The alternative is to make your own, I attach a photo of the stays I made for the L2. The securing fittings are as used in the C types; I believe these might still be available.
George, the only J2 wing main wing stays available now I understand are those for the late swept wing cars. The arm supporting the headlamp is far longer and cranks forwards.