in the U.S I have bought very warm sweaters a winter Jacket , and a rain poncho that all come with a little hole on the top wear A D ring, slips out of easily.
I also tried doggie booties for Suzi but , she slipped right out of them they were a little big. Then i bought infant socks, the tiniest size, and placed a pair on Suzi, and then the booties. I still need to secure her booties on better so I used these little elastic socks that came with her Hallooween costume. She's going as Pochohauntes . That held everything together, but, she did not like wearing them. After all that !
I'd suggest looking on Ebay for those who live outside the U.S . Their are very cute clothes there.
But, shipping costs can be costly .