Lights clipped onto luggage are pretty much always aimed badly, so you want a light that's bright over a large angle.
Lights that are "chip on board" with multiple bare LEDs (i.e. not encased in clear plastic domes) are best, such as these
Planet X clones of the Moon Comet. The Moon Nebula is even better if you are feeling flush, or Aldi sell their clone again.
(note that the 130 lumens quoted for the Planet X is for the white front version - you don't get as many lumens for the same power with red light as the eye isn't so sensitive to it)
The Smart style of light is very directional, and will be much less bright to following traffic that it looks in the hand unless it's solidly mounted, to allow proper aim.