From experience- your best bet with reproduction is to decide on one design you REALLY like and then find a good tailor or seamstress in your community. It costs...oh...several dozen times more than buying a ready-made repro item but you'll get exactly what you want and can monitor the quality throught the assembly process. Buying vintage clothing or having a repro custom done over the 'net can be a headache because you won't know exactly what you are getting until it is too late to turn back.
I have a friend in Tampa who is really good. Tracie Arnold. She has a website called moviegowns.com. There are other sites as well, but I highly recommend you go with a site that has good feedback from buyers because a few sites collect money and give you a cheap knock-off or nothing at all. My friend Rosie tried to buy some gowns from one seller who was a con artist. J. Laconte is a great dressmaker as well. Go to CostumerManifesto.com and find other links to dressmakers and patterns. I make my own, but I'm not that good at it although I'm getting better. I've made about nine costumes now, two inspired by designs of Lucy Duff-Gordon's, and others I found in Edwardian catalogs or Tom Tierney illustrations or other illustrations from that era. The last gowns I made look fabulous, but I know I made many sewing mistakes that I have to improve upon. Although my "breakfast dress" seems to be flawless. But that's my opinion!
After checking out a number of costumer-links at CostumerManifesto.com, I settled on an Indian firm, UJNA Universal (Replicaters[sic].com), to make an Edwardian era army uniform. I initially thought I would find an antique uniform somewhere, but my frame is not exactly 19th century. Plus, if you buy vintage, the garment might be too fragile to wear and enjoy. Kyrila and Jim are right. If you plan on wearing the garment, have something custom made--preferably by a local costumer or dressmaker.