Ribbon cutting/cornerstone laying.
Or maybe they can rent something.
The building is already there. It just needs some modifications. It's going to be in the existing US Consulate compound (look for the Diplomat Hotel on Google maps).
Interesting trivia - it isn't in the former Jordanian occupied East Jerusalem. It is in the former "No Mans Land" between the former Jordanian and Israeli held portions of the city.
Trump has said the modification should be under $250,000.