Since the elastic strap on a pair of good goggles is usually one of the first parts to wear out with use, most skiers would like to be able to replace their straps. Unfortunately, the vast majority of goggles on the market have straps that cannot be replaced. You can still, however, hang on to the lenses and just replace the frame altogether. Sometimes, you can even reach out to the company and ask for a frame – they will probably charge you a lot lower than if you were to buy a new goggle set altogether.
If neither of the previously mentioned options is possible, your only option is buying a pair of new goggles. You will have extra lenses from your last pair as a backup, but you will have to buy the entire new set. This can be a little pricey, but you should not worry at all since goggles need to be worn for a serious amount of time before the elasticity of the strap wears out.