This is the best darning foot for slant shank machines that I've ever tried:
http://shop.sew-classic.com/Singer-S...-SCF384037.htm
No problem at all using it on the 301. I have a vintage darning foot that was made specifically for the 301, but I like working with this one better. :)
Great visibility and very quiet. I have about ten different kinds of darning feet including some that are very old and some that are virtually all plastic and pretty expensive - but my favorite for the low shank costs $3 and this one for slants costs $6. I wish they made this model in a low shank style.
After you've been quilting for a while, this foot almost disappears and you don't even notice it being there! :)