How can I get the Girls' Captain Mills Costume?

There's a costume on Millsberry, called Captain Mills. I really want it!! But there's no one to buy it besides yard sales. And in yard sales, people sell them way too high of a price. So if you could send one to me then my username is rockin_4ever Or if you have one in your yard sale, I'm willing to pay up to 5,000 for it!!