I'm sure many of you have seen this already. In fact, I'm sort of counting on it.
mtdome.jpg
(source)

Does anyone know what that bubble actually is?
Closest thing I've been able to come up with is that its a skylight dome. In fact, it looks very much like the dome found here, although they don't list prices for just the dome (or even if they sell them separately), and the only ones I can find for sale online are much too small for this (only 10 inch diameter).

I'd love to try building one of these for next year if I can find the parts.

Looks like its just the dome, probably using a piece of plywood cut to fit into the rim there with was on the underside to give them a place to attach to, and I'd want to add a covered exit for them on top (a small exhaust cover should work) and some handles to make lifting the top off easier.

Probably need to drill a few holes around the bottom for ventilation and moisture drainage...

Or maybe deviate from this design a bit and put a dowel going down the middle to support a "landing bay" at the bottom. Cut out a circle from the bottom and add a PVC pipe with a wooden base and add an entrance cut into it. That way dead bees would fall, slide down the sides, and fall into the "cup" next to the entrance where they would be easier for the bees to push the rest of the way out.

Then could just add a hole in the top for a normal mason jar feeder and a few ventilation holes around the base of the dome (under the lip there to prevent rain from getting into it), and done.