Hey, Megan!
Welcome to the Disney Parks Moms Panel. Congratulations on your upcoming wedding. I can't think of anything more magical than a princess getting married!
The Mickey Mouse "glasshouse" balloons are a theme park exclusive item and not sold in stores or online. This unique and most popular souvenir on both coasts was first sold in 1996 at Disneyland Park. After speaking with a Cast Member I would suggest emailing Guest Services at guest.mail@wdw.disneyonline.com and pose this same question. There may be a way of getting a bouquet of these "Mickey Mouse in the glass house" balloons for your enchanted day.
Disney Dad Tip 1: Check out
Disney Floral & Gifts for some great idea for decorations and ideas. They do sell balloons here, just not the Mickey "glasshouse" balloon. There are lots of online vendors that see Mickey Mouse head shaped balloons. Just enter "Mickey Mouse balloon" in the search bar and peruse the results. Maybe some come in clear, white or another color that matches your wedding theme color.
Disney Dad Tip 2: I would also contact
Disney's Fairy Tale Weddings & Honeymoons. They may be able to guide you in the right direction.
Megan, enjoy making many Magical Memories and I know you will live happily ever after!
~Jason ºOº