I don’t know if anybody makes a duck tail type spoiler or the rear of the sedan, but I know that RKSport makes one for the coupe. I made a flat plane style spoiler for purpose of reducing aerodynamic drag on my sedan, but I did it in the interest of being cheap and used coroplast, and it looks a little haggard...

for the lip, they sell a product called EZ-lip that attaches with adhesive strips, or you could make an air dam out of lawn edging...

i attached pics of my mods and if you’d like I can measure out my trunklid extension to make a template for you... you might wanna use something smoother than coroplast though(Celtec comes to mind)