I turned this mallet from a branch of Lignum Vitae several years ago. It's all of one piece and weighs 1lb 3oz (540gm).

I love this mallet! It's a perfect shape and weight for medium to light work and sits on its flat top full time on my bench.

You should be able to turn a pretty close copy from this drawing; the measurements (in mm). However: this graphic is smaller than actual size you may want to enlarge and cut out as a template.
Right click on the picture itself and choose "print".

It's unlikely you can get Lignum. You'll have to use the densest wood to get to approach this weight for the size.

A trick: increase a mallet's weight by boring deep holes into the flat end, and towards the centre, fill with lead shot to the weight you want, and plug.