There's a ton of spoliers on ebay. Even the "JDM" 4th Gen style "wing" with 3rd brake light for $86.
As for rear diffuser not many options for 5th gens. But there is one on here that can be 3d printed with the ability to add a brake light. I have the 2 end pieces printed myself but haven't done the center yet. It takes a very long time to print and it's always taking a chance that it will turn out wrong after 18+ hours.