feet are very easy to get - just have to get ones that fit the National machines. You can tell by the shape of the underbraider or shirr plate - though there is always the case that someone may have swapped them out.
This is what the different ones look like for comparison (this is the underside to show the "hooks").
The first fits a White Rotary, the next I believe is an older New Home Rotary, then Free and later New Home Rotary, and the forth is National Rotary (which is what the two spool is). There is another style for Standard that is not pictured here.
FYI - the White and National have the same width gap, but the needle hole is in a different spot, so make sure to check that before you start stitching.
you can do a search on eBay for Greist attachments - then find the set that has the right parts. Very seldom will a seller know what they fit.
There are several generations of parts - with the single, five stich and 1,6,12 stitch rufflers, along with newer sets that have an edge stitcher to use for braiding instead of the underbraider attachment.
And then - you can look for the left/right zipper and left/right cording feet. . . and then the buttonholer (green box fits National) and the zigzagger. . . and the fun just never ends LOL!!