Mine was the exact same thing as your. Do you have the stock line? I sliced the plastic stiffer ofor the stock one and wrapped it in black tape over the new line

 

I have an aftermarket stanless steel braided line that the PO installed. So I don't have the old stock one. I think Lowes has poly air tubing I can try if I can find the correct ID size.

 

If you can't find one at Lowe's, try a truck shop. The airline they use would be the right stiffness. And they have lots of sizes

 

I'd say try some thick wall shrink tubing. Take a look here at www.heatshrink.com and get a size like 3/4" ID that will shrink at 1:3, it will shrink from 0.75" to 0.25" ID.

Click on the data PDF link to see the full specifications. If it can slide over the fitting then shrink it down with a heat gun. It isn't cheap at around $10-11/foot with 4 foot length. Possibly an electric shop or doing a bit more searching can get it local and/or lower cost. Maybe 1/2 or 3/4 ID can slide over the fitting.

 

Both good ideas guys. I do have a big truck stop about 30 minutes away that has everything. That heatshrink would be perfect to hold the slit opened air line, giving it a factory finish. Nice and clean, done the right way. Perfect....Thanks guys.