You can buy simple transfer paper online at Suitup Art Supplies. The webshop for all your creative supplies. Here you will find all sorts of tracing paper on rolls and loose sheets of tracing and graphite paper.
Tracing paper is perfect for use when tracing an image or drawing. The paper shines through a little, so if you hold an image underneath it you can see it clearly through. The traced image can easily be transferred from the tracing paper to another sheet of paper or canvas. Use pencil, so that the image is transferred clearly.