As for WarioWare: Snapped!, because it is a DSIware game, there is no printed instruction manual for it. Instead, all the basics are included with the game itself. If you would still like one though, there is a fan-made instruction manual that explains the basic settings of the game.
However, for Game & Watch Gallery 4, Rhythm Tengoku (GBA), and Osu! Tatakae! Ouendan, there doesn't appear to be anyone selling these manuals at the moment. Even though it may take a while, it would always be a good idea to consistently check the listings on sites such as Ebay, Craigslist, Amazon, etc, for people selling the manuals you're looking for.