The Community of Christ, formerly the Reorganized Church of Jesus Christ of Latter Day Saints have as #253 in Hymns of the Saints keep alive an Advent hymn I like very much, "Heir of All the Waiting Ages" written in by Unitarian minister Marion Franklin Ham. (They have a new hymnal in the works, so who knows what the future holds.) Sung to the lovely tune Picardy, more often matched to "Let All Mortal Flesh Keep Silence."
The 90s-era Quaker hymnal, Worship in Song has it too. I wish it was in a current Unitarian Universalist hymnal; the old red and blue hymnals have it.