See this thread: Arrows
For a rounded-front arrowhead to meet PD rules, it has to be conceptually like a flat-front head with a hemisphere of extra foam on its front (with the soft foam being all one piece, of course: if you were to glue a dome onto an existing flat-front arrow, the glue would be a harder stiffer layer that would raise the injury risk).
I think I might have seen some like that in use, and anyone who makes LARP arrowheads to order (rather than selling from stock) would probably be willing to make them that way.