Am I obliged to pray immediately upon waking during the Necessity Time of Asr, or is it permissible for me to delay it in order to search for a congregation, knowing that I may not find anyone?

If you wake up at the time of necessity and fear that the prayer time will expire, hasten to perform it and do not wait for someone to pray with you in congregation. It is not permissible for you to delay it then, due to the Almighty's saying: "Indeed, prayer has been decreed upon the believers a time-bound ordinance." So, whoever takes it out of its time without a valid legal excuse has squandered it, and the Prophet, peace and blessings be upon him, condemned those who delay it beyond its prescribed time.