Reddit mentions of Brown Bear Full Animal Hood Hoddie Hat Faux Fur 3 In 1 Function

Just the bear arms? If it's not a full costume, this is the closest thing I could find.

This is pretty hard to do, but not impossible to pull off in the time given especially since you want to go reverse annie. I would try to find a cheap bear costume online to get that out of the way for your friend to wear so that you can both focus on the tibbers. You could try doing a larger bear costume but it might be harder to find since you're much taller and could get expensive.

http://www.amazon.com/Brown-Bear-Animal-Hoddie-Function/dp/B005MH6UP0/ref=sr_1_8?ie=UTF8&qid=1405384351&sr=8-8&keywords=bear+suit

http://www.amazon.com/Dress-Up-America-Mascot-Brown/dp/B007XF9EZC/ref=sr_1_2?ie=UTF8&qid=1405384351&sr=8-2&keywords=bear+suit

Since youre wearing a dress you dont really need a full body suit and could just modify either or to try and make it look scarier by adjusting eyebrows adding darker colors too the face fake blood etc etc.

As far as the dress goes you could sew it yourself if you have the know how or even shop for similar items by thrift store or clothing stores and make adjustments accordingly. Luckily for you it isn't a complicated dress. You might have to spend a few bucks here and there but like I said it's definitely doable this is just a start up suggestion for you to build on and get an idea of where to get started. Just focus on getting the most core concept done and then work on the details but most importantly just have fun with it!