Do you mean sleeping aid as in tablets homerbart? I wouldnt buy any medication online, you never know what may be in it.
I would go to the doc if I needed any sleeping aids, at least you know what you are getting is safe and a prescription is probably cheaper than buying dodgy stuff online
I recently spoke to a herbalist as not sleeping well. They advised Passiflora which is not a sleeping pill it just promotes relaxed natural sleep. This seems to be helping quite a bit. Obviously now I can obtain this from Napiers website but would not want to just randomly buy something if not sure exactly what it was.