You could modify the top rear of the bipod sleeve shroud by brazing in place a large stop to prevent the gun tipping over. Then call it an L4A9
Incidentally, although I have not seen anything official, it was tacitly approved to fit the shrouded bipod sleeve to the L4A1's and Mk2 and 3 Brens still in limited service. Later, the same applied to the fitting of the top butt loop for the sling attachment