Greetings Jessica, and welcome to planDisney!
Thanks for sending your question our way. I can sir-tainly assist you on a quest to find the shining armor you're looking for!
Bibbidi Bobbidi Boutique in
Magic Kingdom Park currently offers two knightly makeovers - The Knight Package and The Deluxe Knight Package; the latter includes the full costume I believe you are looking for. You can also outfit your young noble in the adjacent shop without a makeover or across the way at
Sir Mickey's in Fantasyland. Aside from these locations, the full knight costume is not consistently stocked elsewhere in Walt Disney World, but fear not; I have a few ideas for you.
I have learned that merchandise is fluid in Walt Disney World, but once you are on property, Cast Members can call to locate specific items you're looking for. My daughter saw a pair of Minnie Mouse shoes a few years ago, and we had trouble finding her size. A Cast Member at our resort shop made a quick phone call and found them at a store in
Disney's Animal Kingdom Theme Park. Once you've arrived, consider stopping by a merchandise location in your resort or theme park to check on the availability of the royal knight costume.
World of Disney® in
Disney Springs has the most extensive selection of Disney merchandise and is your best chance to find anything you're looking for. There is a wall of princess dresses near the back of the store, and you might also find a royal knight costume here. It's hard to say for sure since merchandise stock constantly changes, so if your plans don't include a trip to Disney Springs, you can always have a Cast Member at another store call before you head over. Other locations where you will find royally inspired attire include Lords and Ladies, Sportsman's Shoppe, and The Crown & Crest in
EPCOT's United Kingdom Pavilion. Even if the royal knight costume isn't available here, you might discover other accessories that fit the bill.
If visiting the theme parks dressed in fairy tale best is a must for your young hero, consider checking
shopDisney as Halloween approaches. The spooky shopping season generally begins as summer nears its end, so if your vacation is still several months away, you might be in luck here, too.
I hope this has been helpful, Jessica, and that you find what you're searching for once you arrive at Walt Disney World. Best wishes for a memorable adventure, and if there's anything else we at planDisney can do before the fun starts, don't hesitate to reach out again.
Have a magical day,
Betsy