I'm not sure what size you are looking for, but Vickey Bishop aka Crafty
Ferret makes really nice ones.  I bought one several years ago and there
is always someone sleeping in it.  It holds two females comfortably but
when the male tries to squeeze in it isn't a pretty sight.  Don't buy the
one from Jeffers.  It's okay but only big enough for a hamster.  None of
mine will go near it.
 
Laurel
[Posted in FML issue 3690]