I got mine here, and they are wonderful:
http://www.metropawlispetboutique.com/buddy_belt.html
The sizes can be tough, BOTH of my guys are "between sizes" - Marcel is between a size 1 & 2 (I have both and am currently using the 1). Wylie is btwn the 3 & 4 - he has the 3.
For ex, w/ Marcel, the size 1 fits him on the very last hole (I could probably do 2nd to last, but it'd be kinda tight); his size 2 has to be tightened to the very tightest, and it's still a bit loose. It is also kinda a pain to put it on the tightest hole bc of the D ring loop of leather - a bit cumbersome. I'd recommend you call Metropolis as well - I know they have given advice to others.