If you would be willing to breed a Modest east sea Shellos I would be glad to trade for it. Oh I forgot to say the ability but that should have been obvious (Storm Drain).
btw I didn't realize this until recently but the Shellos form mechanics changed between 4th and 5th gen. In 5th gen if both parents are a Shellos/Gastro then it uses the form of the mother (no change from 4th). But if one parent is Ditto it uses the form of the Shellos/Gastro. In 4th gen doing that defaults to west sea form.