You contact them, the OEM.
For example, if your interest is in a Cisco branded device, contact Cisco.
If your interest is in a non-Cisco component, used in a Cisco device, contact the component manufacturer. However, on the last, first it might not be easy to identify the OEM for a non-Cisco component, within a Cisco device. Second, often such components are manufactured strictly for a company like Cisco and/or even if not, the component manufacturer might be under contract with a company like Cisco that they cannot discuss that component being used by Cisco.
