I think the Jets are adding a middle six forward and a defenseman at the deadline, more inclined to say 3LD than 3RD, but that could be a defenseman who is currently playing top 4.
Not sure any player off the roster is available, if anyone is it's likely Ville Heinola who could QB a PP, and get a fresh starter as a regular, but he might be kept for that position next year, given the uncertainty.
Jets might put up their 1st this year, if it's the right fit, probably with an emphasis on some term. 2nd next year could be in play too. The lowest draft position the Jets have ever started in is 60th in 2018, so it will be interesting to see if they would go into this year's draft starting potentially in the 90s. In spite of having only 4 picks last year, the Jets look to have found some potential steals in the later rounds.