You can check ebay and Ken's
http://webstore.quiltropolis.net/sto...3&Item_ID=1857
http://www.allbrands.com/productsear...g+foot&x=0&y=0
If you get it from Allbrands, sign up for their newsletter first and get a coupon code ;) They have coupons every month.
Have you looked in stores for it?
If you call Ken's and tell them what you are looking for, they'll get you exactly what you need. They probably sell the Janome brand one as well as some generics and they'll be honest with you about whether it's worth the extra $20 for the Janome brand. I don't know since my Janome came with the walking and 1/4" feet.