There was a thread recently about using a Command strip. To answer your question, I purchased the 1/4 foot similar to this one, but I still had seams that weren't perfect.
http://shop.sew-classic.com/Low-Shan...e-SCF60615.htm
Then one of my vintage machines came with a tool like this, only solid where this on is open. It works for me and is easy to pop out of the way when I want other than 1/4" seam.
http://shop.sew-classic.com/Seam-Gau...l-SCF55415.htm
I wish the metal part that guides the fabric was a little longer, but it works well. You can also adjust it to a scant 1/4 easily by loosening the screw and sliding the bar.
I've been quilting two years now and can't sew a straight 1/4" seam without my guide.
I also tried a magnetic one from my LQS. Ah, the 301 is aluminum so that was a no-go and it could be moved slightly over time on the 15.