Cold iron arrows?

[talino7]

Where can I find this type of arrow to help with fighting demons?

[Aradon]

There are a few quivers you can buy in Kenabras that have limited ammo. When you activate them, your bow is treated as cold iron. I think the blacksmith outside Defender's Heart has several quivers for sale.

Later in the game, when your weapon gets a +3 enhancement bonus, it is treated as cold iron all the time. In the meantime, pick and choose when to use your cold iron ammo.

[Elnidfse]

At the start of the game you can buy 6 from the blacksmith outside. 2 from the very first merchant you see. And I can't remember how many from the random traveling skeleton salesmen.

Look up the Covenant of the Inheritor and how to get it early because that item will change your entire gameplay experience. It makes all weapons count as good and cold iron and gives a +2 to overcome SR for all party members within 30 feet of you.
It's a very good item.