It's not that hard to #imprison #Trump, but everyone in the legal system seems to think it is. Would it cost a little extra money? Sure, but that's minimal compared to the damage he's causing.
Put him in solitaire with his own private guard from the Secret Service or from the prison guard staff. Why would that be any different than any other SS assignment?
Otherwise, build him his own little concrete cell block with rotating Secret Service detail. Or detain him at Guantanamo Bay.