We'll be arriving from Amsterdam to Gare Du Nord. We're looking for accomodations nearby for 4 nights. This will be for mid-December.
Try booking.com for what’s available nearby for your dates and price range. Then maybe ask if maybe anyone has experience with what’s available.
How many are "we"? What is your budget window in euros per night?
There are a lot of excellent hotel/restaurant/cafés options near Gare du Nord, much of the area is composed of ethnic neighborhoods. The areas are perfectly safe, but not as shiny as are some other traditional choices such as St Germain, Latin Quarter, the Marais.
I have stayed and enjoyed at other hotels in the 25 Hours chain, but not the one in Paris. But it's situated just a few hundred feet of the front entrance of Gare du Nord. Warning, their website is absolutely obnoxious and may well put you off. It did me just now.