Hi we have studied this issue before.
 
Here is the only thing we came up with some far.
 
Well you know them small corner litter pans that everyone has too many of
them.  My husband took and put the litter pan in the back left corner of
the med.  size carrier he then drilled a small hole threw the pan near the
top of the pan and the carrier at the same time then he put a nut with a
big head on it and a lg.  washer and pushed it threw both of them, he then
cut off the nut and left a nub long enough to put a nut wing on it on the
outside of the carrier.  You can put lock tight on the washer and
permanently attach the nut and the washer together to it stays attached to
the litter pan.  You can take the pan in and out to wash them, the only
problem is that it doesn't work with the really small carriers.  We now
have pans for each of our medium carriers.
 
Hope this helps someone.
 
If you have a ferret question drop me a line?
I have Ferret Hammocks 4-Sale(2 Sizes)
Ada and Kerry Gibbs
[Posted in FML issue 3026]