With some encouragement (or is it egging me on? :) ) from Russell and Matthew, I'm going to see if I can get the JB Weld repair of the right motor on droid #2 to work. The area where the hole is is not structural - nothing rests on it. The hole just needs to be sealed up. I held off on ordering a new NPC2212 motor for now.
The JB Weld cured, and this evening I removed the tape on the outside.
I whipped up some more JB Weld for a second pass. (I always mix too much.)
I applied it to the area of the hole, and smoothed it out.
I'll let this cure overnight, and then I'll test the motor with a battery. I expect it will work, but the real question is, will it work reliably over a long period of time? We shall see.