Locate a snes emulator and just get double dragon-there isn't much games like that officially for the ds.
Tokyo Beat Down is the closest I can think of to a Double Dragon game as a side scrolling "beat 'em up" game. There is however Double Dragon Advance for GBA if your wanting to play a portable Double Dragon or as mds stated get an snes emulator and play Super Double Dragon. As for a new Double Dragon only one I can see was a launch title for the Zeebo console (released May 2009) but it looks like a port of the original arcade version.