1 to 3 month old? why 1 to 3? why not 3-4 month old? where would you get a 1 month old panther?
if he/she is a tiny tiny guy like around 3.5 inches total length... your best bet is just providing a little plastic tub. put some plastic vines and fiber glass mesh for different girth sizes for grip excercises etc.
getting an adult cage for a 1-3 month old isnt the best idea. help your little guy out and provide him/her with the sized cage above if he/she is around 2.5-3 months old.