Look for used Berninas and Vikings too. I have a Viking Opal 650 as a travel machine. It is over your budget, but it does have a serpentine stitch, and I have learned to really love it for applying binding. I have a sit down quilter, so I don’t use any of my regular sewing machines (a Bernina 440 plus some vintage machines I only sew on occasionally) for quilting anything bigger than a table runner. I really tried to find an inexpensive machine as a travel machine to be used 90% for piecing but also for mending and home dec while in our motorhome, but they just didn’t feel as solid to me or they didn’t allow me the flexibility of stitch length/width or needle position. I got a screaming good deal on the Viking, but it definitely isn’t my 440 in quality. Then again it is quite a few pounds lighter and much easier to haul around.