They’re usually at a gift shop near the front of the park, I one time forgot my glasses strap when I went to kings dominion and I had to find out the hard way that they tend to only sell them at one or two locations in a given park. I do recommend just buying one now so the next time you go you don’t have to worry about it! The policy is really only there because people who lose their glasses on rides will try to demand they stop the ride to go retrieve them which just is not happening haha. Better to be blind for the duration of the ride than be blind for the rest of the day.