Solar Shield Fits-Over SS Polycarbonate II - Kristen Stewart - JT Leroy
The large fit over sunglasses have a black frame and grey polarized lenses and side windows. The glasses in the film have the logo with 'Solar' written above 'Shields'. An exactly the same pair is pictured on the left. It is an older model of the current Classic Ex-Large fit-over shield sunglasses.
Although this seems to be an out-of-production model, you can find these sunglasses on eBay for $10.
Solar Shield sunglasses are made to fit over prescription glasses or readers for convenient sun-protection.
Kristen Stewart plays Savannah Knoop / JT Leroy in the film that also stars Laura Dern.
Reference: Solar Shield Fits-Over SS Polycarbonate II Smoke