  Resonant elastic soft x-ray magnetic scattering (XRMS) is a powerful tool to
explore long-periodic spin textures in single crystals. However, due to the
limited momentum transfer range imposed by long wavelengths of photons in the
soft x-ray region, Bragg diffraction is restricted to crystals with the large
lattice parameters. Alternatively, small angle x-ray scattering has been
involved in the soft energy x-ray range which, however, brings in difficulties
with the sample preparation that involves focused ion beam milling to thin down
the crystal to below a few hundred nm thickness. We show how to circumvent
these restrictions by using XRMS in specular reflection from a sub-nanometer
smooth crystal surface. The method allows observing diffraction peaks from the
helical and conical spin modulations at the surface of a Cu$_2$OSeO$_3$ single
crystal and probing their corresponding chirality as contributions to the
dichroic scattered intensity. The results suggest a promising way to carry out
XRMS studies on plethora of noncentrosymmetric systems hitherto unexplored with
soft x-rays due to the absence of the commensurate Bragg peaks in the available
momentum transfer range.
