I happened to have one light that still lit, but had no liquid left inside, and one like that had liquid with a burnt out bulb. I decided to see if I could make one working light out of the 2 broken bulbs.
This is how the bulbs are supposed to look:
Step 1: Burnt Out Bubblers
Another bulb burnt out, and could probably be replaced, but the base of the bulb is fused into the plastic housing and I don't want to put it back together if its going to wiggle or wobble at all.
Step 2: Swapping Parts
I ran a thin blade along the seam between the 2 colors of plastic. Once the knife gets into the seam, it starts to separate and makes a nice popping noise. If all goes well, the seam will pop open without cracking either piece.
Before you try to glue anything, dry fit the halves of the bulb. There are two protruding keys on the top that fit into depressions on the base. Once you get the top and bottom to fit with a tight seam you are ready to glue it.
I used Krazy Glue, but you could probably use any super glue or model glue.