Please go back and read what I wrote about the pictured MP5 in my first post.I don't think anyone did.
There are some other solutions, most of which have been posted in this thread. I've watched a few reviews on these 'others' none seem much better than iron sights with tritium or fiber optic inserts.
BTW, I think the big fat thingy atop that MP5 is the SAS's early version of a gun mounted 'white light'. It's a flashlight.