I've never ordered anything from Rakuten, however I've been looking at airsoft guns on it, hence knowing where to look for the S&W.
Rakuten seems to be Japan's version of Amazon and Ebay. In Japan, where Rakuten is omnipresent, its businesses include online travel, auction and e-books, plus a bank and securities firm, as well as a baseball team, the Rakuten Eagles.
If you want to go "all in" watch the action site gunbroker.com. You can get the other Indy gun, the Smith and Wesson 1917 for $400-500 if you are lucky/persistent. The hand ejector seems rarer and thus higher priced. Neither will come with 4 in barrels, you will have to cut either one.