Electrical – How to retrofit a junction box in an insulated wall

Typical cold climate construction: Drywall, 6mil vapour barrier, fiberglass batt insulation. How do I retrofit a junction box and maintain the vapour seal? To be clear, by 'retrofit', I mean the drywall is up and I'd like to install this without having to repair any drywall.

Typically for new construction, you'd use an insulated and sealed box:

The vapour barrier is sealed against the gasket when drywall goes up.

Obviously, there's no way to get this box into a wall without removing a large chunk of drywall.

Does a product exist for this? How do you get a box into the wall and maintain the seal with the vapour barrier, without any access to the inside of the wall beyond the hole the box will fill up?

(actually fishing the wire to this box is beyond the scope of this question)

EDIT:

This worked brilliantly.

I cut a square hole out of the existing vapour barrier, then pushed the vapour box in behind it and spread it out. I then used tuck tape to attach from the back of the existing vapour barrier to the vapour box (using several small overlapping pieces), and had enough room to fit in a regular old work box.