This is random but the UBS building in Weehawken has a gift shop in it. Only open during the week. The store is straight out of the 90s. I bet they have post cards still. They did like 3 years ago.

Edit: Best Wishes Card & Gifts

Give them a call in the morning and ask. Last time I was there they had really cool 80/90s postcards. Shocked they still had them on the rack.