I've found ONE head from another manufacturer that fit onto a PanO fusilier (miscast head - rather than wait for a replacement (which would just come with the same head, anyway, and I'm not fond of that head), I snipped it off and subbed a hooded WHFB WE head (it actually is the same scale head).
Haven't found ANY of the PIP heads to fit them though. Not LI anyway. Maybe better luck with MI or HI and PIP heads.