Juliana, the/a company that makes pet mobility carts is
 
K-9 carts        ph. 406-995-3111
P.O. Box 160639,
Big Sky  MT. 59716
e-mail  [log in to unmask]
 
The carts are custom made and shipped usually within 72 hrs.  Prices listed
are $205-$345 US plus shipping, according to the ad.  They incourage you to
call them for advice or problems "...as we are specialists in the care of
the handicapped animal and are anxious to help you and your pet."
 
Give them a call or email and see what they say.
 
Also, I have seen/heard of using hydrotherapy for animals with arthritis
etc.  You may be able to do this in your bathtub ONLY UNDER SUPERVISION.
Put in enough water so that Pauley can't touch bottom and supervise some
swim time.  The water helps by taking the pressure off his little rear end.
If you can manage it, it will probably help.  You could also try massaging
his hind quarters.  I know you can buy a natural product for massaging that
is supposed to help with joint stiffness.  The gentle touch, at any rate,
will make him feel good.
 
IF YOU TRY THE BATHTUB THING, NEVER LEAVE HIM ALONE, EVEN FOR A SECOND.
AND ALWAYS REMEMBER TO DRAIN THE TUB, IT WOULD BE HORRIBLE TO FORGET AND
FIND ONE OF YOUR BABIES THERE.  I know a woman who's boyfriend forgot to
empty the tub after a bath and they found little Phoebe in there the next
day, so please be careful.
 
Anyway, that's all that I can suggest, from one ferret lover to another.
Good luck and Good Wishes,
 
Lara
[Posted in FML issue 2498]