I have the Fokker D7 from Great planes. I used a windshield washer tubing from NAPA. It cost me all of 2 bucks.
Then I took a block a wood and drilled a whole the same size OD as the tubing.. then glue an #11 blade to the block so it would split the tube in open. ran the tube through the block pressto.. the tube is split up. Then with some clear silcone i had just glued to the plane.
not sure if you can see it this picture.