1. Chargers receive pick 29 and 71 from the New Orleans Saints
The best realistic package that the Chargers can get for the 21st overall pick is in a trade-down with the New Orleans Saints. This presents a situation in which the Chargers can stay in the first round and still get a third-round pick in return.
Staying in the first round has its perks outside of just being an earlier selection. It gives the team the ability to pick up a fifth-year option down the line with said prospect. Even if the Chargers draft someone at 29 that could have been available at 35, there is an added benefit here.
New Orleans is a team that has not been shy in moving up in the draft in the past. The team does not have its own first-round pick this year because of it and instead has the San Francisco 49ers pick, which they could use to trade down to the 21st pick.
Even though the team signed Derek Carr the Saints could be looking to bring in the next QB that will eventually take his job in two years. If it is not a quarterback, the Saints have a lot of offensive needs. If there is someone special on the board at 21 that won't fall to 29 they will not be shy in going and getting them.
The 21st and 71st picks have a combined value of 775 so the Chargers, in theory, would be getting the better end of this deal. If the Saints wanted to move up it would not be out of a place of leverage, which could prompt this kind of payment.
New Orleans can afford to do so as the team still also has the 40th pick in the 2023 NBA Draft.