Unless you're planning to attempt to get literature, it may actually be better to go without a badge. I went in a suit with a goatee, no badge, and I was assumed to be an 'unbelieving mate' and greeted with smiles by people who didn't know me. Some of 'em even did so in the hotel! I think somebody even hugged me, though my wife was trying to 'warn' them! This is a huge recruitment draw, a public event like this, so going 'badgeless' works, in theory.
I made a lovely 'Safeguard Your Sparlock!' District Convention badge awhile back. I didn't wear it, but it was pretty cool. Had a little picture of Sparlock on there, my name, and the congregation I got kicked out of.
--sd-7