Hi abannore,
The most realistic CATs available are the 6 from GMAC, but retaking a CAT that you've already taken is NOT a realistic way to assess your skills. Seeing even a few 'repeat' questions can 'throw off' the Scoring Algorithm and impact your pacing, energy levels, fatigue, etc. (meaning that they would likely all be better than they normally would be). Thankfully, the CATs from Kaplan,
MGMAT and Veritas are all 'close enough' to the real thing that they will provide you with a relatively realistic score assessment (assuming that you use the CAT correctly).
If you've studied for (and taken) the GMAT twice - and ended up with results that you were not happy with - then some adjustments to your studies will almost certainly have to be made (far more than just working with a new set of practice CATs). As such, it would help if you could provide a bit more information on how you've been studying and your goals:
Studies:
1) What were your two Official GMAT Scores (including the Quant and Verbal Scaled Scores for EACH)?
2) How long did you study before each attempt?
3) What study materials have you used so far?
4) How have you scored on EACH of your CATs (including the Quant and Verbal Scaled Scores for EACH)?
Goals:
5) What is your goal score?
6) When are you planning to retake the GMAT?
7) When are you planning to apply to Business School?
8) What Schools are you planning to apply to?
GMAT assassins aren't born, they're made,
Rich