Ah yes, the passive aggressive elbow bump "telling" him that he's
invading your space. That'll show him.
Perhaps you could "man up" and just say that you paid for your full seat
and that you would like to share the arm rest? You know... express
your opinion verbally.
Another option is to overtly flirt with him... stroke his arm... and act
completely creepy. That usually causes them to recoil in horror and
could be a more "aggressive" passive aggressive move if one lacks
the spine to actually say ones opinion outloud.