Doors and Windows - Need removable storm door

I live in a small apartment above a bar. It is actually a small house with a store downstairs and one apartment upstairs. There is a staircase leading up one flight. There is a lot of cold air blowing through the front door and up the stairs. Also, there is noise from the bar that comes through the drywall in the staircase. Local codes won't allow a storm door outside. I would like to install a door in the staircase to block some of the cold air and noise. Problem is that the staircase is 32 1/4" wide. Just enough space for furniture deliveries. The door has to be easily removed. What kind of door should I buy and how can it be installed for easy removal.

Thank you.

Amy