Help with overstimulation/public tantrums

My twins are 18 months old (16 months adjusted) and my son gets very overstimulated around big crowds or in places with a lot of noise so going out to eat (or really anywhere these days) is unbearable. His tantrums are getting worse and it's really hard. Does anyone have tips for helping him calm down or toys that you keep in your diaper bag that your little ones find soothing and entertaining?