Had the same issue at a formal 40th just before Christmas. I was informed by She Who Must Be Obeyed that:
1) I am going in a suit.
2) I am leaving my bag and Bat belt at home.

At that point I balked, that's like being asked to show up wearing my birthday suit and a smile.
So I cheated.
Leatherman PS4 and Victorinox Midnight Manager on a dangler chain right front pocket.
Keys, AAA torch and peanut lighter left front pocket.

During the evening, everything except the lighter got used.