Your GMATPrep score is amazing! You're off to a very good start.
I second intellijat's suggestion. The GMATClub Tests
are of very high quality and will challenge you! In total, there are 925 (37 questions x 25 tests) questions. The entire package costs $79, but it's worth it.
Also look into Jeff Sackmann's
Extreme Challenge set. The set contains 100 questions and costs $25. It's a tad pricey, but Sackmann's questions are very GMAT-like. And his explanations are very helpful.
GMAT Club Premium Membership - big benefits and savings