How should I ask politely for a moment of someone's time?
How should I politely ask for someone's time to interrupt them, like in English:
Do you have a minute?
May I bother you for a moment even though you're quite busy?
When I want to interrupt someone in front of me I would say:
Verzeihung, haben Sie bitte mal einen Moment Zeit?
Entschuldigung, darf ich Sie mal stören?
The leading word (not important which one you choose) gets attention to the question itself. To make the question polite, it's important to give it a polite pronunciation. I would not tell the guy that he's busy, he knows it himself.