Nice question! This may not qualify as a definitive answer, but there is a pattern of molecules
that goes under the name Möbius aromaticity, which is at least close:
And this Technology Review article describes a prediction of "a new form of crystalline carbon made entirely of Möbius-molecules of graphene."
Möbius strips have also been formed from DNA, but artificially, as described in this Science Daily article.
And moving beyond the molecular world, there is this:-)
