The best way to hide the seam (you can never completely hide it) is to make the leather piece about 1/8 longer than needed. Then skive (taper) each side to about a 30 degree angle. Then glue down one edge, wrap the tube completely, and overlap the second edge, and glue it down. Use contact cement on the tube and leather to hold everything in place. You can try to cover the seam with lacing, but since the tube is so small, the lacing might overpower the leather work. Using cord, and doing a baseball stitch might work also. You can find books on this at a Tandy Leather Factory near you.
Tom