At one of the Intertoys shops I picked up the mini hexpert, one of a series of six or seven mini puzzles.
It can also be ordered online at https://www.intertoys.nl/iq-mini-hexpert-hersenstichting. Unfortunately 6 of the 7 versions are not available in the webshop.
De hersenstichting is THE Dutch foundation for brain reserach
The degree of difficulty is well chosen. The size is such that it can easily be taken with you in a coat when you’ll be travelling by car or train.
justpuzzles 