I have some downtube braze on cable stops that accept 5mm housing with no ferrule. I made the mistake of assuming they would take a standard ferrule (~5.7mm?). I've set up my barcons using 4mm housing, and the cable is too loose in the cable stop.

Does a 4mm ID, 5mm OD ferrule exist? I can't seem to find any online, and my closest bike shop only had the 5.7mm OD plastic ferrules for 4mm housing.

Am I doomed to buy 5mm housing and rewrap my bars?

Thanks,
- j