(entered for 12.11.05; writer's apology: technical difficulties interfered with posting earlier)

Meaning: not the slimmest possibility. Origins and mentions.
Rewrite 1: not a demon’s hope of heaven
Rewrite 2: not a snow cone’s chance in the ocean
Rewrite 3: not an iceberg’s chance in the Sahara
Rewrite 4: a bat has a better chance in a blinding snowstorm

Comment: Most similarities to ghosts are difficult to parse for a rewrite, so I tended to other, more substantial lost causes.

More reading about clichés
What I found when I googled “clichés”:
• Chester Novello: “Clichés is a prelude, fugue and blues for jazz sextet and has undergone two bouts of revision since its première by the Birmingham Contemporary Music Group in October 2001 (conducted by Pierre-André Valade).”