You can clone dart object easily.

dart_clone_object.dart

factory SearchRequest.fromJson(Map<String, dynamic> json) => _$SearchRequestFromJson(json);
Map<String, dynamic> toJson() => _$SearchRequestToJson(this);

SearchRequest clone() {
  final String jsonString = json.encode(this);
  final jsonResponse = json.decode(jsonString);

  return SearchRequest.fromJson(jsonResponse as Map<String, dynamic>);
}