Third HDD (optical bay) pointers?

Oh dear it's that time again, the bi-annual "crap outta space" time. Good thing it coincides with black friday this year.

Anyway, the deal is this. I'm looking to add a third HDD via the optical drive, since it's to the point where I need access to files while retaining maximum portability (ie I have too many externals). I'll probably end up buying one of the 750gb drives off egg ( Newegg.ca - Seagate Momentus ST9750420AS 750GB 7200 RPM 16MB Cache 2.5" SATA 3.0Gb/s Internal Notebook Hard Drive -Bare Drive) or somewhere else; the problem is where to get the caddy itself.

Someone linked me 2nd HDD / SSD Caddy for ASUS G51Jx, G73Jh - replace optical [OBHD-SATA12-SATA-BU] - $44.75 : NewmodeUS, Hard Drive Caddys for Notebooks , but I'm not sure that a piece of aluminum is worth $50? Has anyone added a drive to their G73 via the optical drive that can give some pointers, like a good place to find a caddy? Also helpful would be any gotchas, and a place to find an optical drive external enclosure (so I can still use it via USB if required).

 

I had no idea this was possible and is really cool! Especially considering I never use the optical drive at all.

Let me know what you end up doing!