Answer
If it is truly impossible to obtain a police clearance certificate, you need to document not merely the difficulty, but the attempts made and an official refusal or the unavailability of the procedure. A simple explanation that “they do not issue it” is usually not enough for an immigration case.
In some cases, fingerprinting and a request through Interpol may be used, but this is not an alternative that the applicant can independently choose instead of a certificate. This route is used when the competent authority specifies the procedure, address, fingerprint form, and next steps.
Collect correspondence, a description of the issuing country’s rules, and evidence that there is no relevant mission or, if applicable, a refusal. Do not use forged or purchased certificates: this creates a risk of refusal and legal consequences, even if the rest of the application is prepared correctly.