Hello, and welcome to ITKE. Almost any of the Cisco exams that start with the number 642- will re-certify your CCNP. If you look on the Cisco certification tracker it will list all of these, which include some of the wireless exams, as well as many others. With only just over a month to go, I would not recommend that you try to learn a completely new subject, and then pass the exem. So I would advise you to stick to something you already know about and pass an exam in that subject. There is also a minimum time that you have to leave between taking the same exam, I think this is one week, so your time is even more restricted if you need to have more than one go at the same subject.
Anyway, I wish you good luck with the exams.