Lot of great resources out there. There are some talented folks on the site here that could probably help you out. If you're looking at sewing your own (I have no skills) then definately check out the Imperial Officer boards.
The base pattern will be a modified Mccall's 4745 costume. Do a search for Char Tozad on the IOC forums, he has some tutorials on what you need to do to modify what ya need.
get in touch with Chris Adams on our forum here. his handle is cblackthorne. he makes very nice officer uniforms, and might be willing to help you out.