I got one of the Fenvi caddy's from an eBay seller named Segoo. I paid about $20 for it and it works perfectly fine. My only gripe with it is that it doesnt have the mounting screws to hold it in place inside the laptop, but I'm not too bothered because when its installed, its a pretty tight fit. That and the fact that it hold my SSD drive, so even if it were to rattle around ever so slightly, the SSD drive wont suffer.
Its recommended to keep the HDD in its primary bay anyway, I've been told it has some kind of anti-shock mechanism.
Anyway, the MCE stuff is a ripoff.