This is the cover I have for my 99K. It was among the accessories. It's luckily pretty common. I don't know if a 99 is the first choice for freemotion but it's possible. It's all about getting the tension right, so far I have managed to darn pretty well with a spring type presser foot. There's an equivalent for the older 15s (with out the drop feature), but I think it's slighly different shaped.