How do I cut off water from a radiator?

[Bogdan Gabriel]

Ok, so recently I moved in to a dorm. I live in a small room, but with a huge radiator, that looks kind of like this:

but with that knob on the upper side. Problem is that the knob is missing, and I can't turn off the water.
It looks like this:

Any idea how I can turn it off by hand, or how I can remove the knob from another radiator and mount it on this one? The temperatures are like hell, and I can't sleep because of how hot it is. Please help.

 

[Plumber69]

If you can rig something up to have that pin held pushed in. Like a couple big zip straps