Reddit mentions of Footloop Shirt Stays with Locking Clamps - BLACK (2 PIECE)

Looks like a great start! I can really only suggest minor things given the work you've already done. :)

1. Press/iron the shirt. It'll look worn on its own as you wear it around.
   
2. Get some shirt stays. They'll keep your shirt looking tucked in.
   
3. Be knowledgeable about the weapon prop policy at the convention center.
   
4. Even though it's not on the reference picture, I think you'd look better with the tie tied a bit longer. Could just be personal preference
   
   Keep it up!

I highly recommend these shirt stays. All the other ones I've tried slip off and snap you at random points during the day. Yes, these do make a tiny (pinprick) hole in your shirt, but it's definitely worth it.

There are also stirrup-style versions that have a loop at the bottom, and you hook under your foot instead of attaching them to your socks. These are the ones I have and they work wonderfully.

If they catch on the inner lining of your trousers while walking and make a thwack kind of sound, I've found that putting your socks on over them, instead of them over your socks, fixes the problem.

I wear these. The only issue is that they show if you aren't wearing black socks. I might get a pair that just clips to the socks. The thing I really like about these is that the clips are VERY strong.

I always just bought mine at the local Military Clothing Store (on base), but a quick search on Amazon found quite a few - I'd suggest these.