Hey Josh,
I am not sure about the GMAT Prep CAT exams re-setting after you take the two tests as I have only taken them once.
As for additional CAT exams, here are a couple more resources that won't cost you an arm and a leg:
1) Veritas Prep - if you buy just one of their books (each is $22), you get 5 CAT exams as well. On another note, if you buy the whole Prep Series Collection, they will give you 17 CAT exams. So unless you're looking to go through a whole prep course and fork over a lot of $, I would go for one volume/5 CATs at $22 (that's what I am doing as well)
2)
Manhattan GMAT - same deal as Veritas except they will give you 6 CAT exams. I took the
Manhattan GMAT course so I already completed these and they are pretty good. The Quant is even a little tougher and prepares you pretty well for GMAT Quant.
3) 800score.com - you can purchase 5 CAT exams for $25. It's also worth noting that of Veritas's 17 offered CATs, 5 of them are from 800score.com, so make sure not to buy both (unless you want to) because then you would be getting less bang for your buck. I have not taken a CAT exam from 800score.com so I can't vouch for their accuracy.
Hope this helps and all the best in preparing!