ETA: Thanks so much for everybody's concern.
We put out 25 color flyers this afternoon. We went to 4 vets' offices nearby, including his own. We posted a couple in the nearest pet stores. We put some in shopping center. A lot went out on the road their street comes off of, then some went in the neighborhood near their house.
Ex is very grateful for me doing this. Boomer's special to me, too, so it's the least I can do.
Funny, as we were out, J commented that he's glad I'm doing this, because he knows his dad would never do it. I guess I've earned me some much needed brownie points. When I told ex J's opinion, he said J's earned himself a future konk on the head. (But J's right!)