Old hymnals are a great source of Mother songs, often having a section in the topical index dedicated to Mother. One that is still in print and has at least 7 mother songs is Heavenly Highway Hymns (Stamps-Baxter Music, P.O. Box 4007, Dallas, TX 75208).

Here is one of my favorites. I may post more later.

TELL MOTHER I'LL BE THERE
(Charles M. Fillmore)

When I was but a little child how well I recollect
How I would grieve my mother with my folly and neglect;
And now that she has gone to heav'n I miss her tender care:
O Savior, tell my mother I'll be there

Chorus:
Tell mother I'll be there in answer to her pray'r
This message, blessed Savior, to her bear.
Tell mother I'll be there, heav'n's joy with her to share
Yes, tell my darling mother I'll be there!

Tho I was often wayward, she was always kind and good;
So patient, gentle, loving, when my ways were rough and rude;
My childhood griefs and trials she would gladly with me share
O Savior, tell my mother I'll be there

When I became a prodigal, and left the old rooftree
She almost broke her loving heart in mourning after me;
And day and night she prayed to God to keep me in his care;
O Savior, tell my mother I'll be there

One day a message came to me, it bade me quickly come
If I would see my mother ere the Savior took her home;
I promised her, before she died, for heaven to prepare;
O Savior, tell my mother I'll be there
--Charles M. Fillmore