How would you ask your professor to be your supervisor?
To make the answer formal, yes, you should ask him. This is best done in person, and one of the best approaches is just what you say here about his skill and your common interest in a topic. Let him know that you think he is the best person around to do this, and you won't have a problem, yourself, if he can't be at the graduation. 

What you need is his signature, I assume, and not his physical presence to approve your completion. 

He might say no, but if you don't ask, the answer is certainly no. 

Good luck.