I've just bought a Lephanthes calodictyon and a pear shaped bubble like yours to grow it in
I bought it from a columbian nursary at the RHS London show on Saturday. The bubbles they had look identical to yours so I guess it may be the same people.
I'm really nervous about growing this one, but had to give it a try.
How are you watering them these days? I was wondering about spraying, or pooring water in, then pooring out the excess (which is what I did to wet the moss before I put the plant in and it seemed to work).