This Hasselblad metal lens shade #40118 for the 80mm Zeiss Planar works perfectly. I attached two very thin metal brackets on the sides to hold masks for portraits and special effects. It's a very useful and simple way to avoid buying expensive filters. I got the idea from an article in an old issue of Pop Photo. You can choose to ignore the modification if you don't use special effects filters.
$40 + $6 shipping