Considering I've never had any issues with that company I can't complain. It seems like if one person in a community of people have a bad experience with someone that means that all experiences will be the same, i'm just here to say that I had no problems with it and it works fine for me so that is not the case every time.
https://retro-spec.myshopify.com/products/retro-spec-280z-260z-240z-downforce-rear-spoiler
I have the fiberglass version on mine, attaches with two bolts that you have to drill. It fits pretty good for what its worth.