Bell (and Soto) are probably the only remaining off season trade pieces for a rebuilding team. Harris next in-season trade deadline if he's back and doing well. You have to fish for guys who are denied arbitration like Hunter Renfroe was last year, bring in a few surrounding veterans comparable to Harrison last year, and hope you hit on a few in-house solutions (C, 2 infielders or an infielder and center).
As it turns out, last year there were a lot of productive, useful, cheap corner outfielders that signed for 1 year guaranteed - Duvall, Schwarber, Pederson, Rosario have all been useful. Haven't looked, but I have a feeling there may be a 3rd tier SS that could be picked up for short years and money.
The line up can be patched, cheaply, with some upside. It's the pitching that is harder to get to acceptable levels, I think.