Where can i buy Eragon's sword?

no where the movie did not come out so never

the answer above is false the movie did come out as to were to buy a sWord idk

The "Brisingr" was never in the first movie, as Eragon had not had it crafted until later in the books. The sWord present in the movie is the Zar'roc ; which

was previously owned to the Dragon Rider Morzan.

I don't know where but some sWord crafters might be able to be commissioned to make it. Pictures have been released of it so it wouldn't be all too difficult.