Instead of looking for unregulated pharmacies, use a legitimate, accredited telehealth platform (such as PlushCare or similar virtual primary care services).
Omnicef only treats bacterial infections. It will not cure viral infections like the common cold or flu. Taking it unnecessarily renders it useless for future real infections.
Once you have a legal prescription, you have two safe options to fulfill it online: Buy Omnicef (cefdinir) Online - Blink Health