I don't know how realistic you would like to go with the wig, but amazon has some pretty good options! You could straighten out this one, or maybe this if you want to keep it more cartoonish and less expensive? (Though the second wig certainly will be a thinner wig than the first...)
I totally understand wanting to save on the outfit, but if you're willing to spend more on the wig (I do that, because I have wigs that work for multiple cosplays) I recommend looking at Pose Wigs for a realistic blonde (esp for the black friday discounts). They're pretty nice quality and fairly realistic