Since the temples are at both sides of the eyes and safety googles have to cover both the front and side areas, I think "lateral" could be used instead of "sien", and I know that soft-touch is not exactly the same as flexible but it has the same purpose and it can also be soft as opposed to rigid. I have used safety googles and never seen any with "almohadillas", although they may exist of course. Maybe you could even say "con protectores laterales flexibles", your context will help a bit here if there is any kind of description. Suerte.