Since you still want an Incineroar-themed username, I think you should try using either Fuegro (its German name) or Félinferno (its French name), since both haven't been taken by an account yet.
Also, I think it would be cool to see French and German language Pokemon names get used more, because I do feel some are very cool. I mean, Wicked3DS actually used Greninja's German name (Quajutsu) as a username at some point, so it's definitely not unheard of.