So I've recently upgraded the groupset on my cannondale caad8 to the 11spd 105 5800 group.
Everything is working great but I've ended up without a barrel adjuster for my front mech as the gear cables are now routed under the bar tape where as the external routing on my old setup had the adjuster at the shifter end of the cable.
Its a bit annoying as I now have to readjust the front mech by undoing the pinch bolt to re-tension the cable and cant really fine tune it.

I'm looking for advice around adding a new barrel adjuster to this setup.
The downtube boss for the cable is non threaded and the cable ferrule is held in by the cable tension.

I've had a look online and seen people talking about threading this boss to install a threaded adjuster and other solutions that require splitting of the cable outers to install an inline adjuster as part of the cable outer.
Id prefer something simple that I can simply install into the current cable boss but I'm not really sure what my options are.

Anyone else been in this situation before and have some advice?