Amazon has
3 Pack Samsung Galaxy S9 Screen Protector PET Soft Flexible TPU film
https://www.amazon.com/dp/B078XRVBYV
or
3 Pack Samsung Galaxy S9 Plus Screen Protector [Case Friendly] PET Soft Flexible TPU film
https://www.amazon.com/dp/B078XRFXZ3
For Price: $4.76 if you use BN7DCOHX