Assuming that you're applying this cycle and can't'delay no matter what, this is what I would suggest. Quit all your commitments and go all out studying for these next 4 weeks. Also, it would help if you could say what minimum score you're aiming for (ie high 20's) and where you're at (ie low 20s).
The practice exams you could buy are 7 Berkeley Reviews, 10 Gold Standards and the TPR cracking and review series ones from their books (their course has some of these same ones). To save time, you could just do the science sections of GS and spend the rest of the day going over content. Let's say doing all 10 takes you 2 weeks. The last 2 weeks can be spent doing aamc's every other day to every 3 days, with rest the day before the exam.
You would probably be better off delaying until 9/11 or until next year, but maybe try something like the above if you have to take it on your current date. If you end up delaying until next year, you'll probably forget most of the studying you've done so far. So don't commit and waste aamc materials if you're unsure of postponing or not.