  We investigate the elastic normal modes of two-dimensional media with broken
time-reversal and parity symmetries due to a Lorentz term. Our starting point
is an elasticity theory that captures the low-energy physics of a diverse range
of systems such as gyroscopic metamaterials, skyrmion lattices in thin-film
chiral magnets and certain Wigner crystals. By focusing on a circular disk
geometry we analyze finite-size effects and study the low-frequency shape
oscillations of the disk. We demonstrate the emergence of the Rayleigh surface
waves from the bottom of the excitation spectrum and investigate how the
curvature of the disk-boundary modifies their propagation at long wavelengths.
Moreover, we discover a near-cyclotron-frequency wave that is almost completely
localized at the boundary of the disk, but is distinct from the Rayleigh wave.
It can be distinguished from the latter by a characteristic excitation pattern
in a small region near the center of the disk.
