Julius Randle
Julius Randle might become available without a sign-and-trade if the Lakers acquire LeBron James, unless he or whoever else he brings is acquired through a sign-and-trade and Randle has to be a piece that is sent in return.
However, if he is available to be had, even though he has some noted locker room issues, Randle would be a very good defensive power forward, while also apparently developing into a solid offensive player as well (Randle averaged 20.6 points and 9.2 rebounds from March 1, through April 10 this past season).
His biggest drawback is that he is not a 3-point shooter, making only 25.7% for his career and only 22.2% in the 2017-18 season, a career-low.
Once again though, he undoubtedly would be an upgrade at power forward over what the roster has right now, and for the right price might very well be available in free agency.