1. Costume

Only a tailer may help here but sometimes cheap solutions can be found in the Internet.

2. Boots

You may get some cheap military boots. They may be also used for other costumes like the X-Wing-Pilot or Tie-Pilot

3. Insignias

Just cut a nice piece of aluminium and attach it with velcro to your costume. Get some 5 mm transparent plastic-plates and cut out the buttons that will be painted only on the backside either red, blue or yellow. Then glue them onto the aluminium. But be reasonable. Don't give yourself too many buttons I think its rather stupid if you go to a con filled with hundrets of.  Super-High-Warlord-Terror-Grand-Moffs.