RE Aviator - Zac Efron - Baywatch
Efron wears the Aviator model with 23k gold frame. It's hard to see which color lenses are in the frame, it looks most like AGX lenses, but could be grey as well. This model sunglasses can be recognized by their bayonet temples, that are designed to fit comfortably under headgear.
Buy RE Aviator sunglasses online on Amazon.com, Amazon.co.uk, Randolph Engineering, or eBay. There are different sizes, colors and temples available, so make sure you get the pair of your preference. Zac Efron seems to wear the largest variation of the glasses.
Randolph Engineering Aviators are almost identical to American Optical Aviators, on which they are based. The American Optical glasses are cheaper, find them on the American Optical website, Amazon.com or eBay.
Reference: Randolph Engineering Aviator, gold frame
In the same film, Dwayne Johnson wears a pair of gold Sama Syd sunglasses.