I have a 2016 GT Grade alloy, which uses full-length cable housings. The front derailleur cable passes under the bottom bracket and up through the frame between the chainstays, where it has a rubber boot that minimizes water & grit thrown from the rear tire getting into the cable housing:


Front derailleur cable boot
The boot is deteriorating and has started to tear. I contacted GT customer service and they have no information whatsoever about this part. My local bike shops didn't have anything that would fit, either. (A brake cable boot won't work because one end isn't big enough to fit around the flange on the frame, and the cable end is sized for a brake cable, so it won't fit snugly around the cable).

Searches for derailleur cable boot or shift cable boot have turned up nothing. Does anyone know of a source for a replacement? Thanks.