Sadly there is no easy solution to this problem, as only supervised time should be allowed for out and about time.
First, should your landlord not allow pets, then the following isn't going to be easily doable.I strongly would urge you to take your squirrel in a safe cage to a family or friend's home for a few days till it all gets sorted out. I wouldn't allow your squirrel to wander around your appt.as they could lick the spray, and chew which since this is an apt. could result in a serious damage fee to fix.
A premade all wire cage with 1/2 inch wire fabric that is large so it can have branches (places) to climb, a nest box to make your squirrel feel secure would be the only alternative if you can find one.
If not then building a cage with 1/2 inch wire gage will be needful could make individual panels 6 of the carried into your apt. with each in turn covered by a sheet as to not advertise you have a pet. Assembling it is easy to do when two holes placed within about 4 to 6 inches near the ends of the panel wood frames by using threaded bolts and wingnuts. The hard part is making the door panel to make a door. This is the design we used in our squirrels cage. I will see if I can get a picture for you of this. The minimum size is 4 by 3/2 ft by 4 ft tall; 4 x 5 is better.
The really difficult issue as mentioned is for a squirrel that hasn't been limited to a cage as they wiil chew the wire which can result in an injury to their mouth and even teeth causing a life threatening condition known as Odontoma, a costly procedure both monetarily and on the animal. For this reason the larger the cage the more comfortable your squirrel will be spending time in it.