I have both feet for my slants.
What foot fits the 401A will fit your 301A because I interchange feet on both my machines.
Order this foot for free motion quilting from sewclassics or from Ebay (the more expensive one, not the less cost efficient $4.97 or $5.00)
Slant shank daring free-motion foot- all metal with clear, marked base. Fits Singer 401, 403, 404, 500, 503, and the Singer 301. (401A, 403A, 500A, 301A, etc.) Click for more details.
The clear base is marked with a grid for precise spacing of stitches.
You will love it's performance.