When my 1981 serger finally gave up the ghost, instead of replacing it, I purchased a foot for my Janome sewing machine that cuts off the fabric. I use a knit-type zig zag (can't remember the name of the stitch) along with the this foot and it works great. Sews slower than a serger, but I dont make many garments these days so this works well. Mine is similar to this:
http://www.amazon.com/Side-Cutter-Se...er+sewing+foot