I came across these sites & was told that they actually got the costumes from a site like Cafepress, but order bulk & send the costumes to shoppers themselves.

http://www.80stees.com/products/Supergirl-Costume.asp
http://www.dressingupboxonline.co.uk/productmore.asp?cat=139&prod=1624

Do you have tried Zazzle and Spreadshirt ?

I already have a Spreadshirt account, but they don't have any.

I'm starting to think that there isn't one.

Do you've checked with zazzle? BTW why not contact directly to cafepress, possibly they can make some arrangement for you.

I've checked Zazzle & I've been with Cafepress before. Not fond of them.