Polymorph it into a Knucklehead Trout (from IWD:RotF)
Disclaimer: First off this requires your GM to agree that Planar Binding can be cast on a Polymorphed Fiend, or a Fiend that is Polymorphed for some of the casting time.
The spell Polymorph specifies "a new form", and that "The target's game statistics, including mental ability scores, are replaced by the statistics of the chosen beast. It retains its alignment and personality", so it depends on whether your GM consider 'type' to be a Game Statistic - and if they do, whether your GM allows you to cast it on a Fiend that remains within range for the duration but spends some amount of time in the middle as a Beast, or even is still a Beast when the spell ends?
I'm going to be assuming that the Planar Binding spell works as long as the target is a Fiend at the start of casting OR that Polymorph doesn't remove the Fiend typing from the Dybbuk, with a note on what to do if it needs to be a Fiend at the end of casting, but this shouldn't be considered a flawless RAW solution.
Before the main event, someone begins casting Magic Circle with a 4th slot, for 2 hour duration (1 Level 7+ caster), just in case.
Once Magic Circle is complete, 3 Casters all Ready spells, or ready the casting of spells for the one with a long cast time, with various triggers.
One (level 7+) will cast Summon Greater Demon as soon as the others are ready (this is basically just to ensure the turns happen in the right order).
One (level 9+) will start casting Planar Binding, with the trigger "When the Dybbuk appears".
One (level 7+) readies a Polymorph spell, with the trigger "When Planar Binding starts being Cast".
When one caster completes Summon Greater Demon they can issue it a verbal command that it must obey for at least one turn, as it makes the Charisma Saving Throw at the end of its turns. Therefore they can order it to accept the Polymorph spell readied, with the trigger "when the Planar Binding Spell starts to be cast".
The Dybbuk doesn't make the Saving Throw to resist Polymorph as it's a willing target, so the spell's caster polymorphs it into a Knucklehead Trout, which is the creature with the lowest Charisma Modifier I can find (-5), from Icewind Dale: Rime of the Frostmaiden, although the Quipper from the Monster Manual has a Charisma Modifier of -4 so is a close second.
While Polymorph is up, the Dybbuk can't cast spells, doesn't have it's Magic Resistance, and has such a significant modifier that a decently statted caster could maintain control over it (the control from Summon Greater Demon) in that form, as its max roll is (20-5), so 15. You should also just put it in a bucket of water, physically restraining it and keeping it from dying (which would revert it to it's normal form).
After 1 hour Planar Binding completes, and since Polymorph was cast after Planar Binding it can still be in effect.
If your GM considers the Polymorphed Fiend a valid target, it now makes a single Charisma Saving Throw, with the same -5 Modifier.
If they insist that the Dybbuk must be a non-polymorphed Fiend at the start and end of the spell, the caster of Polymorph can drop it just before the spell and it makes Planar Binding's save with a +2 modifier and advantage from Magical Resistance.
If you've maintained control via Summon Greater Demon you could potentially try and order it to accept the Planar Binding and fail the Save but that's not a RAW option.