JQ+ has a website
http://enthuware.com/jqplus/ The simulator costs something like $20. at the beginning I was a bit confused to see many typos (like "seperate" everywhere), but the codes and comments are very helpful and professional.
I also heard a lot about JCertify and other codes, but never tried them, I know that they cost above $50.
If you train 1 or 2 weeks with such a simulator, taking, say, 1 exam a day and analizing and fixing ALL error answers in detail and if after this time you have above 75% on NEW mock exams (there are 8 in JQ+, smth. like 500 questions), your chances on a real exam will be substantial. It was critical for me, but if you have 10 years of C++ experience, maybe you can do without it. It depends.