Okay, so I had to look up the character first because I'm not familiar with her!
But I think looking at thrift stores as well as Target would be a good place to start! Fall is *FINALLY* here, so all of their cute clothes are out now on display! Even Walmart has some cute sweaters out I've seen, so you might want to take a look there as well! Anything that can work that won't cost you an arm and leg is perfect in my book!
And if all else fails, you can always check out Amazon! They're wicked awesome with their two-day prime shipping!
Good luck girl and I hope that you're able to find everything that you need!