Good thinking about that light panel -- thanks!
In other good news, over on Amazon I found "Triocottage-Specific Accessory Rotating Wheel That Drives Turner's Movement" and it does, in fact, fit perfectly in this HHD model, hurray! And the motor seems to be turning the wheel as expected...
So I managed to pick up one of those cheap 12-egg incubators (sold under lots of different brand names, or none at all) -- just like this one:
And I bought it for a song, which is great, but it's somewhat incomplete, which is not so great, but possibly not a big problem. It's easier to list...