I cannot make one myself
Mothers with sewing machines, and little old ladies down the street, can do wonders.
don't have the money to pay the prices they are getting from the sell-off of uniforms used in the series.
Buying from the "It's a Wrap!" eBay auctions, with the intention of wearing it as a convention costume, is rarely going to help. The chances of being the exact size of the person the costume was tailored for
, and then maintaining that size
yourself every time you wish to wear it, would be next to zilch. Not only that, you wouldn't be game to eat while wearing it.
As I inferred earlier, part of the reason actors (usually) look so good in their costumes on screen is that they have fluffers who are continually checking. A convention floor costume has to be comfortable and capable of passing close scrutiny over a longer period.