I would suggest attaching casters to small wood blocks (say 2" x 2") which
could then be easily attached to a wire mesh cage with brackets.
 
Also, there are models of casters available which don't have the vertical
shaft attachment, but instead have a flat top with screw holes.  These
are normally larger in size, however, and might not look as nice.  One
advantage to the former solution is that the wood blocks can be easily
painted to match the cage.
 
Good Luck.
 
 
******************************************************
Chuck Steel
[log in to unmask]
http://www.andrew.cmu.edu/~csteel/
Windows Software Specialist, Applications Software Group
SNZS568
 
"Experience is what you get when you don't get what you wanted" - Unknown
[Posted in FML issue 3075]