I would make the Invoker parallel to the Cleric: WIS-based caster with a Deity and a Domain, but getting all spells through the Domain from the Wizard list. That is, you could have each Domain say, "Even if this spell is not on the Invoker spell list, it is an Invoker spell for you."
Damage types: Lightning, Psychic, Radiant, and Thunder would parallel the 4E Invoker best. You might have to create a whole new set of spells, though. There is much precedent for that: WotC has been creating new 5E spells since they announced the game -- Fire Bolt and Witch Bolt are new ones, for examples.
Transmutation and Conjuration would be flavorful if you get around to creating dedicated Invoker spells.