There's players available who can help. It would depend on who is or isn't in a playoff position around the trade deadline. Gustafsson, DeAngelo are options as they're likely on non-playoff teams, Demelo is a cheaper option but we won't know the whole market for another few months.
And they are not going to throw away this season, they would go for a rental, especially one they could possibly re-sign for two seasons after this. We will have cap (and good taxes and a solid team) for the next two seasons to sign a veteran free agent/our rental to a competitive price. And then cap for Hague when that contract expires. Or if we trade for a younger defenseman they can sign to a reasonable, more long term deal they can do that and trade someone later.
The Flyers, for example, have picked up two of their top 4, RD even, for Gudas, a 2nd and a future 3rd. Either one of Niskanen or Braun would be very good for our top 4. You can get a good defenseman if you look.