Create an in-world Health Bar using Materials?

Hello! I am trying to create a health bar for a character that will be displayed on the character’s weapon, rather than displayed as an HUD element. What I have set up now is that the player’s health being reduced will cause a panner to move the texture down on the Y axis. However, if the texture is wrapped, it just pans downward with the top connected to the bottom. When the texture is clamped, it stretches. What I would like it to do is have the texture move downward, leaving an alpha behind, until it completely disappears when the player’s health reaches zero.

How would I go about doing that?