Helmut has one for sale...even with a similar crack on the right side
https://www.weitze.net/militaria/74/Mecklenburg_Strelitz_Pickelhaube_fuer_Einjaehrig_Freiwillige_im_II_Bataillon_des_Grossherzoglich_Mecklenburgisches_Grenadier_Regiments_Nr_89__388074.html