Same rockers and oil feed as me. As far as I know these were A7 longstroke only.
I have tried fiber washers, dowty washers, copper washers and various silicone and they all did not work.
Since I have just replaced the rocker spindles I have now taken some grinding paste and lapped in the banjo to the spindle, and the banjo to the oil feed bolt. Then used a very small amount of wellseal compound (
http://www.wellseal.co.uk/) on the surface faces and bolted it all together. Just enough to make a good seal and not cause problems with the oil feed holes in the bolts.
(I am a big fan of this wellseal product - worked wonders for me on other issues and a mate of mine who maintains a fleet of classic Rolls Royce swears by it. (product was developed by Rolls Royce)
I only did this last night actually and plan to ride on saturday - so by then will know if my plan has worked.
Pic attached of the rocker box and spindles without the banjo / oil feed in place.
I will update pic and results later on how this has worked.