Polo Ralph Lauren PH4098 - Khalid Abdalla - The Crown
The glasses are worn on the yacht in Episode 2 and in the car rides in Paris. The glasses have a dark tortoise frame, the word POLO on the left lens and the Ralph Lauren logo on the temples.
You can also find these on eBay but they costa bit more there.
Khalid Abdalla plays Dodi Fayed, Diana's lover who died alongside her in the 1997 car crash.
Reference: Polo Ralph Lauren PH4098