The blue and green beasties behind my boy are garden variety ukuleles, available at nearly any music shop. Ukes can be strung left or right handed.
I was tempted to get him a left handed electric mandolin. But those things, despite their size, are pretty expensive. The guitar he’s got in his lap was less than 100 euros, and it’s 3/4 size. Still too big for him, but he’ll grow into it.