How do you get a newt?

By waiting until they come to you.

Newts in general are a protected species so cannot be bought legally from any pet shop.

Your only hope is to build a pond in your garden and wait, I did this and now we have frogs but newts are not so easy to encourage, unless anyone has any ideas.

Get one from someone who doesn't want theirs anymore. They can live for a very long time.