It takes a village to regress a little.
My roommate went out for fast food the other night. Unasked, he brought me back a kid's meal.
I was planning to go to a haunted house event with a friend. Unasked, she made sure to check if I wanted to do the "no scare" day.
I was playing a game at a friend's place. When other guests arrived, they all spoke softly to me and joked about how she was "basically losing to a two-year old."
None of these came fully out of nowhere. I had talked to them each about my regression, and been small around them each before. But once they know you as "the little one," it becomes part of how they see and treat you. It's not just a separate fact, some bedroom lore, but just who you are as a person to them.
Safety comes first, but if you know you will be? Consider telling your trusted, consenting friends.
Once you do, will you ever really be big again?