It's most likely a Davis made machine (Though Sears reused the name after they stopped using Davis to make them). If that is the case, getting a shuttle will cost $10-$20, and it's not that hard to do. Needles may be another matter . . . you can get a few and then only use the machine for light work so you don't break them often.
I figure that is what I'll do with my machines that are hard to get needles for - I'll save the heavy work for the Singers since getting needles for them is simple and cheap.