A walking foot for a 301 was never made, that is the only foot that Singer didn't make for a 301. The slant shank walking foot fits zig zag slants so its "foot" is too wide for the straight stitch 301. However, Sew Classic modifies the walking foot she sells so it fits on a 301. The reviews are mixed, some people state it works fine and others say it doesn't.
Like everyone else has said, the 301 is a fantastic machine. Prices for them have been jumping up there in the last couple of years due to their popularity though, so be patient and watch for a good deal unless you have a deep pocketbook.
Cari