You won't be able to buy Simon's goggles anywhere. You'd have to make them by scratch. My suggestion is to make the goggles out of craft foam and clear yellow plastic sheets.
[~Future Cosplay Plans~]
Bill Cipher [original human design] (Gravity Falls)
Mabel Pines (Gravity Falls)
12th Doctor [Female] (Doctor Who)
Wirt (Over the Garden Wall)
Montreal Comic Con 2015