Shader that does per Vert alpha with co

I am trying to wrap my head around this shader stuff and know what I want but can't figure out how to translate it to the unity shader stuff so I thought I would ask here.

Essentially I am trying to use the color specified by the property but still use the alpha component of the per vertex specified colors.

So the final pixel color would be PreBlendedColor = Color( _Color.R, _Color.G, _Color.B, vertColor.A )

 Properties 
 {
     _Color ("Main Color", Color) = (1,1,1,1)
 }

 Category 
 {
     Tags {"RenderType"="Transparent" "Queue"="Transparent"}
     Lighting Off
     BindChannels 
     {
         Bind "Color", color
         Bind "Vertex", vertex
     }
     
     SubShader 
     {
         Pass 
         {
             ZWrite Off
             Cull Off
             Blend SrcAlpha OneMinusSrcAlpha
         }
     }
 }