Assuming you can find(or ‘make’) a large enough window, anyone capable of putting up scaffolding can tack an elevator shaft onto a building/wall/etc. for temporary purposes.
Expensive? Quite probably. Within the budget of someone who would pack two elevators when travelling? Also quite probably. And definitely way cheaper than trying to add an internal elevator shaft to a building not already provided with one.
Still doesn’t explain why you wouldn’t just choose a building with a preexisting elevator; but some mysteries remain for the ages.
