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.
That's what I'm thinking, or an old one that hasn't been used. Apparently the person that swiped my old name left to another site already so I'll waiting 4 years to get it :V