I just found a reference to a book which has the text of Vin Garbutt's The Gunman.

Title         The Oxford book of English traditional verse / chosen and edited by Frederick Woods, Published Oxford ; New York : Oxford University Press, 1983

The book is in an Australian university library collection but I'm sure other libraries would have a copy.

Also I did a Google search on the search terms:

Garbutt "Mr Gunman"

and there are a few vinyl records available for sale.

I had the pleasure of seeing Vin Garbutt perform at a small concert in a pub in Newcastle NSW Australia many decades ago. He was amazingly brilliant.