Have you checked out Prissy Paw Fashions? I have bigger girls too, and Cynthia has made them lots of really cute outfits for very reasonable prices.
Here is a strappy ruffle vest that says Mommy's Girl (view embroidery options):
All About Stripes
She also has a lot of cupcake and birthday dresses if you browse the site. Here is one of the birthday dresses:
Happy Birthday Dress
You can ignore the "out of stock" you see. She custom makes everything to your dog's measurements, and if it is on the website that means she has the fabrics available to make it.