Stitchnripper

I was happily sewing along when the little button stopped working and machine took off. Had to pull plug. I opened it up and don't know what I am looking at except that little metal piece was floating around inside. I think it goes on the part that controls the button, but, there isn't a screw in there to attach it.

Is this something I can fix myself or should I order a new one, and if so, from where and what? it is for my 401A.

Thanks in advance. You all always come through for me.