Hi and Welcome to YT!
I find that hoodies or pj's are the most comfortable for my yorkies and keep them the warmest.
Check out
Washable and reusable dog and puppy pee pads, belly bands, and diapers at T. Bumpkins & Co. AND
FuFu Fashions custom dog clothes and apparel for great custom pj's, this way they will fit perfectly and be even more comfortable.