I didn't think there was any "head bob", except perhaps while sprinting.
I expect it's some sort of 1st person animation, so I think if you could fid out which one and perhaps replace it with an empty animation you could disable that.
Alternately, it
might be governed by a game setting, although I think that's quite unlikely.
Hopefully someone else more familiar with animation can give some more useful advice.
Cipscis