Find something wrong with the jumpseat and MEL it. Is the fabric torn? That's a fireproofing hazard. Is the cushion worn, that's a safety hazard as well since the seats are certified to withstand a certain G load in a crash.

I used to write up pilot seats because they were so worn out it would hurt my back. Mx will be forced to MEL the jumpseat.

Bleed the oxygen down to a level you can only depart with 2 people in the cockpit.