Hi,
Needles, shuttles, and bobbins are not as easily found as Singer but available online. Proper needle is 20x1 or Boye 14 which is longer than common Singer 15x1. Some lower the 15x1 in needle clamp as a 20x1 replacement. The shuttle and bobbins are Boye 13 or sometimes found in a used lot. National was a very common machine and lots of wearable parts if needed are out there, just sort of have to know what your looking for. With any luck your National will have it's shuttle and a few bobbins included. Good Luck.
Jon