Datel Games 'n' Music would be recommended, as you can find it at Wal-Mart near you . Cost is around 20$, and the box contains also a 128 MB microsd card.
Oh, and remember that it doesn't support commercial DS roms, and it's Slot-1.
I'd recommend the M3 simply from consoleup.com (£23.99 without memory card) and Sandisk 2gb microSD from play.com (£13.49). Recently recommended these to other UK users and they have been happily playing Monkey Island ever since
The M3 simply comes with a card reader and a protective case for the DS-game-sized unit, so you can keep it safe and nothing protrudes from your DS during use.
There are frequent system updates so you can probably ignore the files on the CD and get the v1.06 firmware from m3adapter.com or a community site like ds-scene.net (a benefit of the community sites is an RSS feed so you can see when the updates are released, they also announce ScummVM within a few hours of it becoming available...)