If you are looking to add or change the look of the 3 , Front lip, rear spoiler , side skirts, rear bumper lip,
front grill... locally RacingBees is a good place to start : https://racingbees.com/search?page=2&q=mazda+3
If you are moving in that directions it will get you thinking of what you like and dont like and want. It did with me.

For the Gen 1 & 2 ... Project Motorsport has some really nice front splitters https://project-motorsports.com
It may help me plow in the winter not sure if im game for that front look. Not sure if it will create more drag than downforce.
I do like the Canards and ordered some . https://project-motorsports.com/shop...-gen-2-canards

Strafe Design also sports some nice front splitters for the Gen 1 & 2 and nice rear diffuser. I ordered it with the tucked
blades . https://www.strafedesign.com/collect...-rear-diffuser
Strafe said it will work on non speed and sedan. It may look odd on my single exhaust sedan, im with function 1st.

As for rear wings on the hatch and sedan. I never could find something that is fitting for the sedan shape.
Project Motorsport has a cool Speed3 rear wing extender : https://project-motorsports.com/shop...on-mazdaspeed3
Racing Bees is a good start if you want to add a spoiler to your hatch or a rear lip to your sedan.
As for my Gen 2 sedan i was always enamored with Ducktails spoilers and that look on a MX5 and RX7.
I eventually found and installed the Krotov Ducktail for the Gen 2 Sedan. Its unpainted black abs.

What do you have on your car ?