Simple answer: if it isn't published, you can't have it because it isn't balanced.
Even simpler answer: Anything your DM will allow is game.
Real answer: There are several ways to get feats, or the use of from magic items. Robe of the Archmagi gives spell penetration (sort of). Inteligent items grant the use of feats from combat reflexes to expertise. Specific magic items can grant anything. Certain creatures, like the Creature Collection II Arcane Symbiote grant feats as well.
Answer you want: there isn't any clear material on this. Forging the metamagic rod as ring would be straight forward (mostly). Other applications you would need to work out something with the DM.