Suze,
Good Eye!!
The (inverted) cage is indeed a second Glamos cage, with the 4 legs cut off (I don't need to attract a lightening strike).
However, now that the heavy duty Glamos cages are difficult to find (and expensive) you can take ANY cage that has an 18 inch diameter hoop, and affix it to the base cage with zip ties. Home Depot in our area is now carrying the lighter duty 18" by 54" tall 4-leg cages, and they would work fine for the inverted cage.
Raybo