Source stones are expendable items. Download the attached file for a PDF of all the magic stuff I've created!
Source Stone: While called a stone, this boney item is actually a gland that can be found in most beasts that are capable of using a breath weapon. Obviously magical, the source stone contains the essence of the element the owner utilizes. With a bit of creativity and some arcane or natural knowledge, that essence can be transferred temporarily to a piece of equipment. When used on armor it acts like a long-lasting resistance potion. When a weapon is treated with it, all the attacks are imbued with its element until the effect wears off; in both cases, that amounts to about a day. In addition, when used on a weapon, once per encounter, you may choose to add 3d8 elemental damage to an attack, hit or miss.
Elder Source Stone: A lot like a normal source stone, except these can only be found in very powerful older dragons, the kinds that have names that people know (and probably fear.) Using these potent stones requires the kind of knowledge that only a specialist would have, and it'll likely cost gold and perhaps even a favor or two. The effects they cause on equipment is permanent; however, the process is incompatible with true magic items, only mundane weapons and armor will work. On the bright side, it will give the receptacle the champion tier default bonus a magic item of that type would have, along with the fancy elemental bells and whistles. And you get to name it yourself!