Just to close the loop on this, I couldn’t find any locations in Cancun Hotel Zone area that offered NAAT tests. Many of the places I checked (Ahorro Pharmacy, JW Marriott, Marriott) didn’t even offer a PCR test! I took a PCR test at the Westin Resort which cost me US$90. I got my results in about 10 hrs.
There was also this place along the beach which I could have used, I guess.