Have things happen around The Source or at the Maesto'D's place of business. I mean, you can literally start scenes by saying something like "So, you're all at Saffron's place hanging out when Been and her gang show up looking like they have a mind to hurt some folks."
Apocalypse World certainly encourages proactive PC action, but if they won't take it, it also definitely encourages you to have things happen to them. Make their lives not boring, remember? And IME, when stuff happens at their place, a person who owns that place rapidly tries to get control of the situation, both in the short term and the long term. I mean, if people want to take over your stuff, you need to go deal with that situation rather than just sit there.
Both are also community leaders in a sense. Have members of said community act on their threat impulses, doing stuff to each other that any good leader would deal with, then the PC will either have to deal with it, or deal with people not treating them like they're in charge any more.
Once you've done this stuff a bit, they'll probably start being a little more proactive in order to stop such problems before they really begin.
You do have a slight issue in that you have two such people. Are their places anywhere close to each other? If not, it gets harder to get both of them involved in the same thing. For future reference, I would've encouraged them to say that the Maestro'D's place was within the Source's area, just to avoid that problem, and would suggest you might do something similar in future...but that's little help with the current issue if they're far apart. Maybe give them mutual enemies? Or make one's ally the others enemy. That helps either bring them together or brings them into direct conflict, both of which are good.