I have a great thunderblade that is really good for stunning enemies such as silver bokoblins. I know a way that may be able to repair it, but I want to know if there are areas where they might respawn.
Thunderblades can also respawn in the Coliseum, just north of the Great Plateau. See my answer about where to get frost blades. The same answer applies for Thunder Blades (+ spear) and fire weapons as well.