Browsing through some scrap parts, I found four perfect plastic spacers. I suppose they were parts of some packaging for sensitive components. The magnet fit right in the 10 mm middle whole. They are just a bit thicker than the magnets are. The resulting small gap reduces the magnetic attraction, thus eases the handling of the magnets.
The spacer was good, but I needed some part on the top end of the new magnet.
I decided to use old 100 Lire coins from the 1970's. Lire used to be the Italian currency up to 2001, when it was replaced by the Euro. I had some coins left and they are litterally of almost no value. The front side of the coins is quiet pretty, showing the Roman goddess Ceres with an olive tree.
The 100 Lire coin's diameter is just a little larger than the spacer, allowing easy pickup from the pinwall.
I just glued the parts together, although the magnets stick on the ferromagnetic coins, anyways.
Some hints before starting to work with the glue:
I decided to glue all magnets in the same north-south direction, giving the option to stack them later on. I used a pen to mark the right direction.
The coins do not have a flat surface. So I used plenty of a rather thick universal glue. It just filled all the gaps.
I tried to center all parts as good as possible.
I let the glue dry for 24 hours with some weight on before first usage.
4 rare earth magnets - diameter: 10mm , heigth: 5 mm
4 spacers - plastic parts from the scratch box
4 attractive coins - 100 Lire worked perfect for me