Sell short an equal-delta amount of the underlying (U).
If U declines while the LEAP is still active, the net value of the position will likely increase, bc the delta of U will decline and its IV will likely increase.
Not sure on this, but I think the $ from the short will be available to you for new positions.
Of course if U has huge decline below the LEAP strike, you could conceivably lose money, and you'd have to do some position mgt, but if it is really DITM now, a net loss on the position may be low probability, esp if you manage it to prevent a loss.
Once the short U opens, you could also put in a limit order to replace the LEAP w/ a shorter duration call, to hasten closure of the entire position. Since you've already got the U short for a delta-neutral position, you can wait patiently until an acceptably tight spread becomes available on the duration change order. Once that order goes thru, you'd then of course close the short U.
Actually, once you get the short U in place, any of the other option strats mentioned could be executed -- the delta-neutrality of the position will free all of those executions from having to accept a poor spread on the option transaction.