I do not trust in ANYTHING aftermarket (atleast not in the price range of the average enthusiast) for such a vital suspension component!
Also, unless they are "correcting" suspension geometry, apart from the bling factor, its almost a waste to ever want/purchase a set..........
However overkill engineering made several sets within a good price range a few years back, but they have since gone out of business and were hit or miss.
Other than that, if you want a custom setup like Kojima, it's gonna cost money and you NEED to get the geometry CORRECT! Any proper fab/race car shop will make you a set. Several hundreds are involved, but most race teams are more than capable of producing a proper set.