Sprite Deform Diffuse Shader

Hello

I'm trying to apply vertex deformation on diffuse lit sprites. I know about the incompatibility between vertex+fragment and surface shaders. One version would be to add Lambert pixel shader implementation but I was unable to find that anywhere.

I need your help :)

Below is the code

 Shader "Awesome/Sprite Deform Diffuse Shader" 
 { Properties 
    { 
     [PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {} 
      _Color ("Tint", Color) = (1,1,1,1) [MaterialToggle] PixelSnap ("Pixel snap", Float) = 0 
     _Frequency ("Frequency", Float) = 1 
    _Amplitude ("Amplitude", Float) = 0.1 
    _UVPercent ("UV Percent", Float) = 0.3 
 }
 
  SubShader
  {
      Tags
      { 
          "Queue"="Transparent" 
          "IgnoreProjector"="True" 
          "RenderType"="Transparent" 
          "PreviewType"="Plane"
          "CanUseSpriteAtlas"="True"
      }
      Cull Off
      Lighting Off
      ZWrite Off
      Blend One OneMinusSrcAlpha
      CGPROGRAM
      #pragma surface surf Lambert vertex:vert nofog keepalpha
      #pragma multi_compile _ PIXELSNAP_ON
      #pragma shader_feature ETC1_EXTERNAL_ALPHA
      sampler2D _MainTex;
      fixed4 _Color;
      sampler2D _AlphaTex;
      float _Amplitude;
      float _Frequency;
      float _UVPercent;
      struct Input
      {
          float2 uv_MainTex;
          fixed4 color;
      };
      
      void vert (inout appdata_full v, out Input o)
      {
          float4 vert = v.vertex;
          if(v.texcoord.y < _UVPercent)
          {
              vert.y += _Amplitude * abs(sin(_Time.y * _Frequency + vert.x));
          }
          
          v.vertex = vert;
          #if defined(PIXELSNAP_ON)
          v.vertex = UnityPixelSnap (v.vertex);
          #endif
          
          UNITY_INITIALIZE_OUTPUT(Input, o);
          o.color = v.color * _Color;
      }
      fixed4 SampleSpriteTexture (float2 uv)
      {
          fixed4 color = tex2D (_MainTex, uv);
 if ETC1_EXTERNAL_ALPHA
         color.a = tex2D (_AlphaTex, uv).r;
 endif //ETC1_EXTERNAL_ALPHA
          return color;
      }
      void surf (Input IN, inout SurfaceOutput o)
      {
          fixed4 c = SampleSpriteTexture (IN.uv_MainTex) * IN.color;
          o.Albedo = c.rgb * c.a;
          o.Alpha = c.a;
      }
      ENDCG
  }
 Fallback "Transparent/VertexLit" }