When I found these being cheaply sold by the case I snatched them up for us! These are rectangular and 12.2 in x 13 in x 23.2 in.
 
Having an emergency butterfly cage is so useful - I use mine when rehoming baby spiders and with feeders, especially in fruit fly accidents (to my boyfriend - this has never happened, I swear).
 
I'm not marking the price up on these because I love you guys! :)