I have a aimpoint mount that fits the MP5/94 series and also the 91 but you have to remove the rear sight on the 91 which is why I am selling it. It is brand new and I mounted my aimpoint on it then set it on the receiver to find out it didn't work unless you pull off the rear sight.
$85.00 shipped. They sell for 100 to 110 from different places. SOLD
I can send pics.