There part number is 5119K11 for 1/8" ID, 1/4" OD viton. $3.22/ft
Greaseworks is cheaper at $3/ft -
http://www.greaseworks.com/store/product_info.php?cPath=27_43_45&products_id=214
They also have a injector return line kit with a viton endcap, as well as kits for the whole car -
http://www.greaseworks.com/store/index.php?cPath=27_41