If the Donks feel they need a big, imposing wall to protect them from angry peasants, I'm pretty sure they could get some assembled, but not yet installed, wall sections sent to Washington from the U.S.-Mexican border. The same company would probably be happy to install them, and throw in the White House at a nice discount.
Elon Musk would be able to add a high speed vaccu-tubs between the WH and the capitol, and maybe even an extension to an undisclosed location to quickly evacuate everyone who matters in case of upheaval.
I can just see the city block sized hole in the ground with cranes sprouting from it, and a big sign on the corners announcing: "On this Site will be constructed a $200,000,000 undisclosed location. Thank you for your patience during this construction."