Can you still write or talk? If not, having something premade and understood by others can be helpful. That could be have a note pad that explains how you’re overwhelmed or holding onto a specific item or hand signal that you’ve discussed with whoever you’re with ahead of time. When I do X that means I’m overwhelmed and need Y.

If you can, talk to people beforehand about what signs you can use to communicate with them in the moment, like keywords or phrases to let them know it's happening

Let your close ones know the signs. If you can speak, have a code word, or even a code gesture, or something completely different and unique to you. For example, carry a penny in your pocket and hand it to someone and have that mean "I'm overwhelmed and I need X"

i usually will write a text!