Adding Alpha to a Shader?

Hey Guys, I want to add Alpha to this shader but I don't know how :/ Could you edit this shader to add alpha to it?

 Shader "N3DS/DoubleSided/VertexLitCullOff" 
 {
 Properties
  {
     _MainTex ("Base (RGB)", 2D) = "white" {}
 }
 
 SubShader 
 {
     Tags { "RenderType"="Opaque" }
     Cull Off
     LOD 80
     
     // Non-lightmapped
     Pass {
         Tags { "LightMode" = "Vertex" }
         
         Material 
         {
             Diffuse (1,1,1,1)
             Ambient (1,1,1,1)
         } 
         Lighting On
         SetTexture [_MainTex] {
             constantColor (1,1,1,1)
             Combine texture * primary DOUBLE, constant // UNITY_OPAQUE_ALPHA_FFP
         } 
     }
     
     // Lightmapped, encoded as dLDR
     Pass
      {
         Tags { "LightMode" = "VertexLM" }
         Cull Off
 
         BindChannels {
             Bind "Vertex", vertex
             Bind "normal", normal
             Bind "texcoord1", texcoord0 // lightmap uses 2nd uv
             Bind "texcoord", texcoord1 // main uses 1st uv
         }
         
         SetTexture [unity_Lightmap] {
             matrix [unity_LightmapMatrix]
             combine texture
         }
         SetTexture [_MainTex] {
             constantColor (1,1,1,1)
             combine texture * previous DOUBLE, constant // UNITY_OPAQUE_ALPHA_FFP
         }
     }
     
     // Lightmapped, encoded as RGBM
     Pass 
     {
         Tags { "LightMode" = "VertexLMRGBM" }
         Cull Off
 
         BindChannels {
             Bind "Vertex", vertex
             Bind "normal", normal
             Bind "texcoord1", texcoord0 // lightmap uses 2nd uv
             Bind "texcoord", texcoord1 // main uses 1st uv
         }
         
         SetTexture [unity_Lightmap] {
             matrix [unity_LightmapMatrix]
             combine texture * texture alpha DOUBLE
         }
         SetTexture [_MainTex] {
             constantColor (1,1,1,1)
             combine texture * previous QUAD, constant // UNITY_OPAQUE_ALPHA_FFP
         }
     }    
     
     // Pass to render object as a shadow caster
     Pass 
     {
         Name "ShadowCaster"
         Tags { "LightMode" = "ShadowCaster" }
         Cull Off
         ZWrite On ZTest LEqual Cull Off
 
         CGPROGRAM
         #pragma vertex vert
         #pragma fragment frag
         #pragma multi_compile_shadowcaster
         #include "UnityCG.cginc"
 
         struct v2f { 
             V2F_SHADOW_CASTER;
         };
 
         v2f vert( appdata_base v )
         {
             v2f o;
             TRANSFER_SHADOW_CASTER_NORMALOFFSET(o)
             return o;
         }
 
         float4 frag( v2f i ) : SV_Target
         {
             SHADOW_CASTER_FRAGMENT(i)
         }
         ENDCG
     }    
 }
 }
 

normally it should look like this:

but it looks like this:

thank you!

EDIT: I tried to use Alpha Cutout for that but it is not supported by the Hardware I use. Is there another way to add alpha to this shader?