Apparently my google-fu is weak today, I'm looking for some tubing to slip over a shift cable for a front derailleur. The cable routes up from under the BB, through a hole in the frame, and out a hole at the top of the BB shell, where the chainstays meet the shell.

It doesn't run clean and rubs on the side of the hole, and I'm wondering if running the cable through a short piece of tubing would be smart. Would maybe need 2-4" of tubing. The front derailleur doesn't get shifted as much as the rear, so it may last a while before replacement.

Does anyone have a source for this, or a few inches they wouldn't mind dropping in the mail for good karma?