I carry Celltei carriers on my site (
www.ImaPreciousPup.com), the tote-o-pet seems to be more popular, I suppose because it looks more like a purse when carried, but the pink crocodile pak-o-pet is really cute. I like it because you can put it on the front seat of your car, it is easy to travel with and the petite (and the small with some airlines) can fit under the seat.
Petite: 11"(L) x 6.5"(W) x 9"(H)
XS: 12.5"(L) x 7"(W) x 10"(H)
S: 14"(L) x 8.5"(W) x 11"(H)
M: 7"(L) x 10.5"(W) x 11.75"(H)
Thos are the sizes, I think most yorkie would fit in the petite or XS.