Your Kenmore is very similar to my 1803 - if you look under the bed on the front edge, there should be a metal plate that says "158.XXXXX" and the first 2, 3 or 4 digits after the period are the common model name.
My 1803 is the best free-motion quilter in the herd - and it does so many neat things, you'll be amazed.
You can find complete sets of attachments and design cams and feet on eBay for $30-40 including shipping. (the shipping is the most expensive part)