Can you recommend a prayer to enlist the divine realm’s help to overcome illness as well as to promote and maintain health?

This again is laudable, because if people do not care for themselves and see to the needs of health and well-being, they will fall by the wayside and little will be accomplished. So you can use the prayer: “Source Creator, help me keep my body safe and strong in all ways by making healthy choices, and seek those things that reward and support a long and happy life. Correct all inner discord and signs of illness within, according to my highest good.”