How to add Unbreaking IV without it being OP

Unbreaking VI would make it so your tool is unbreakable BUT you can't use it when it gets down to 0. You could repair it later with an anvil. You could only find this enchant in woodland mansions very rarely (Maybe a 3 percent chance).

Let's say you were mining and you had an unbreaking 4 pickaxe and it got to 0 durability, normally it would break but with unbreaking 4 it would just stay at 0 and be unusable (It would be like mining with you fist if you tried to mine with a 0 durability pickaxe).