2 Options:
1. Buy the caddy model that fits your laptop, they're not all the same.
2. Buy a USB to SATA external enclosure. Cheaper, but more cumbersome since the drive will be outside of the laptop.
This illustrates the Lenovo solution - the Ultrabay (developed by IBM.) I have never hear of Acer having one.
3rd party makes them for various notebooks.
The one I bought from Hong Kong for my Thinkpad T60 worked at first, then wouldn't close. Shaving about 1/64th inch of plastic off two nubs seems to have fixed the problem. The tolerances aren't huge. I think I paid around $12.I got a generic 9.5mm caddy for my drive off ebay for 16$. I just installed it but it's not perfectly flush against the system (sticks out 1mm) and I may need to drill some holes...