I bought the blue dress 11 years ago, and I wear it to death in the summer, as a housedress. Each year, it gets flimsier and flimsier, so, I decided to make a clone. I copied it, using a beefy cotton/poly knit. The blue dress is very thin, and drapes accordingly. The pink knit is new and thick. It is a less flattering drape, accordingly, but I don't care. In 11 years, after hundreds of trips through the washer and dryer, I bet it'll drape just fine. The fabric is a "Juliette" knit from Ressy's Co-Op. (See Yahoo Groups to join - once you get involved in Ressy's Co-op, you'll have access to some wonderful finds.)
To copy is simple. If you've never done it before, a garment like this - a simple knit with not too many design lines - is perfect to start with.
Take the source garment, lay it on a table, which is covered with paper (I use old blueprint paper). This garment was done in three steps. Front, back, and sleeve. For each step, lay the garment flat. Methodically press out the wrinkles with your fingers. Then use a tracing wheel to mark the paper. You have a pattern sans seam allowances. True the pattern, add seam allowances, and hem allowances, and it's done. There are many sources available to help you learn how to make patterns from finished clothing. And Threads Magazine featured an article on this recently, too. My husband, Nick, gave me the book by Rusty Bensusson, many years ago. I used that to get a 'handle' on the process, then graduated to more technical references, later.
So...you'd think I would discard my old faithful blue dress, now that I've got a pink replacement. But I can't bear to part with old blue. So now I'm wearing both. Maybe I will get another 11 years of both garments?