Does anybody know where to get hold of a set of these ? Mine has been lost when I had the cylinder head done 
I worried about those myself because one stuck in the head and the others remained in the block. I managed to remove it from the head an set it in the block, where they remained safe.
But to your question, I would measure the holes and look for a steel pipe with the correct diameter and a 1/8" wall thickness. As I recall they are appx. 2 cm long. Edges slightly beveled.
If hou have a lathe make your own.
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