I've tried Netherite ingots, Gold ingots, Gold rings from this mod. Only thing left is to make another piece and use that to repair, but that's too costly to be worth it. Is there any material that can repair gilded netherite pieces through the anvil?

Also on this topic, there is a nice feature from another mod "netherite extras" which allows converting netherite ingots to nuggets which may be used to repair with the anvil, enabling the gilded netherite items to benefit from that mod's item (maybe not the chestpiece since a nugget is way smaller than a chestpiece armour).