half moons should be still available the thing to watch when fitting the new gasket is when you tighten down the cover the gasket can tend to spread at the fwd corners in at the cam bearings due to the new half moons compressing and forcing the gasket outwards.you can avoid this by puting a very very light skim of sealant on the metal surface of the head and sit the gasket into position making sure that it fits snug into the bearing corners (i think there is little locaters on the gasket) then let it set.
next put the half moons in position on the head and put a dab of sealant in the same corners because this is where it will leak, then tighten the cover down evenly bit by bit in a pattern like a head bolt sequence.when all done after its been running check in the spark plug cavities because if the gasket leaks in there it will fill up and cause a weeeee missfire and the n when you go to remove the plug the oil pores into the piston