Do not doubt me, Lord Vader, this IS the song. Bruce was a moderately successful recording artist and released this on 45 in 1964. My copy is, at present, packed at my mother's, but it was the first single I bought as a child and I loved it. I used to know the words by heart, but I am now a bit vague on the middle. However, the last couple of verses are as follows (I can find no trace of this record on the net either):
I can remember when I was a boy,
That my bed was a ship that I sailed through the night,
And I remember the world was a place,
That was eager and loving and shining and bright.
Where is the boy that made friends with a rainbow
And once rode upon'
Where is the shy and mysterious person
Oh where have I gone?
I can remember I once said my prayers,
Now I stand by while my children say theirs,
Watching them kneeling,
And I could cry that one day they'll forget,
All that they're feeling,
Isn't it sad that our children should grow into people.