HARMONI is the first light visible and near-IR integral field spectrograph for the Extremely Large Telescope (ELT). It covers a large spectral range from 450nm to 2450nm with resolving powers from 3500 to 18000 and spatial sampling from 60mas to 4mas. The IFS Pre-Optics (IPO), sub-system under the responsibility of the Institute of Astrophysics of the Canary Islands (IAC), contains 30 opto-mechanical mounts working at cryogenic temperatures and are classified into three types depending on the mirror shape: [1] - Sprung kinematic mount for flat mirrors: By spring loading, the mirror is constrained radially against a Vee-groove. - Thermally compensated kinematic sprung mount for power mirrors: It is similar to the previous mount but the radial pads compensate mirror radial movement. - Bonded mount for toroidal mirrors: The mirror is bonded to a rear invar pad, which serves as an interface to the support. This work describes the designs developed for the opto-mechanical modules of the Instrument IPO in order to comply with the sub-system requirements. We also present the prototypes developed to prove some of the adopted concepts in the design.