If the step-in style isn't working for you, you might try a harness vest/dress. There are several vendors here at YT that offer them. Check the Yorkie Items for Sale forum. I absolutely love the style and workmanship of YT member Connie. She has a huge selection and is wonderful to work with. Here's a link to her website
http://conniedressmydog.com/ or you can just send a pm to Connie and she'll fix you right up.