Right now I see it on Amazon with a notice that if you order in the next 5 hours it could be delivered by second day (Sunday?) for Prime members. Where you see this the option frequently exists to have the item overnighted as well -- for how much will depend upon whether you are a Prime member or not (overnighting an item isn't terribly expensive for Prime members, but can be for non-Prime, on Prime-eligible products). You may, or may not, have to spring a little extra for Saturday delivery, however -- you would have to complete a mock check out to learn all the shipping options and details/pricing.
Otherwise you'll need to find out where your nearest Authorized DeWalt Service Center is located as there is a decent chance they will have one in stock (but call ahead to verify availability and Saturday hours).
Or you could ask to borrow some time on a fellow member's thickness planer to finish milling your lumber while you wait for the replacement -- odds are good that someone will step up if the request is made as it is a great way for both of you to meet a fellow woodworker in your area.