Hey there! I'm super duper sorry for the late reply! I'm not sure if you're online or not, but I wanted to let you know that I'm still interested in the items! I've been busy offline and I haven't been checking notifs and I apologize for never giving you an update!
no, storm drain is really your best shot at making it worth your while carrying gastrodon in your team.
also remember, that gastrodon is in a lower tier than a lot of pokemon,so don't be surprised when it get killed by a lot of pokemon