How to repair a cloth item in Divinity: Original Sin EE?
Normal armor and weapons can be combined with the repair hammer but this is not the case for cloth items like leather armor or head caps.
Solution 1:
As long as you have 1 point in blacksmithing and possess a repair hammer, anyone linked to the character with those two things can repair any item of theirs, armor, weapons etc.
There isn't a separate item or skill to repair differently named/style items or apparel.