Well, I was wrong. They apparently did make walking feet for the slant machines. Here's the
etsy page for different slant shank walking feet, including both vintage and new ones.
As I said before, I have one that is labeled Singer and one that has no label (both were bought new in the last 5 years). I bought another one because the Singer model didn't have the little arm that you use as a guide for echo quilting. I probably bought mine from Sew-classic, which is now out of business, but they are
readily available lots of places. I think I paid around $20.00 each for them.
bkay