nadie95,
If you haven't replaced it already, I believe a presser foot thumb screw will work on the stitch length lock dial. They normally have a tiny metal and fiber washer under them as well. I've seen them somewhere, if I run across them I'll post the location. You might try Jenny at Sew-Classic, if she doesn't have the screw and washers she might could get them. Also try your local sewing machine shop.
Joe