Walking foot definitely get the Bernina one but expect to go into sticker shock. It is super expensive. I saw your post in pictures so I'm not sure if this machine takes the older style feet or the newer ones. A bernina dealer will be able to tell you and order in the proper foot.
I use my quarter inch foot more than any other, I would probably go name brand on that as well. But also spendy, not as bad as the walking foot though.