You could consider a Kiton suit, 7-fold Tie (or Hermes?)and or wallet. BRioni, PRada, RL Purple Label? (note, handmade suits take a while to produce so be aware of your timing).
Pick up a pair or two of Allen-Edmonds shoes.
For other advice you could check the
www.askandyaboutclothes.com forums.
Does your job require you to dress up frequently?
Is the event white tie, black tie, casual etc? If it is an outdoor summer event you may have to pick up a light coloured linen suit, but that would not provide a lot of alternative uses for the outfit.
I frequently deal with people in the 8 and 9 figure range, but most of them don't dress that flashy. What line of work is the individual in?
I would caution against spending too much on any one item (for fear I would be afraid to wear it again), but try and spend a lot on accessories that could be used to enhance other outfits that I would regularily wear.