The N48 specification is merely an indication of the magnetisation quality. The strength of a magnet depends on its shape and size as well as the respective magnetisation quality.
For magnets of the same size and shape, a higher magnetisation quality (indicated with NXX) means a higher adhesive force.
You can find more magnets with a very specific magnetisation here: Magnets N35, Magnets N40, Magnets N42, Magnets N45, Magnets N52