A few weeks ago, I wrote about the G-Tech G-Connect iOS NAS drive. It is a 500GB 2.5" NAS that allows you to stream videos to iOS as well as act as a micro AFP file share / TimeMachine server. It has onboard ethernet as well as Wi-Fi built in. They routinely go on sale for $39.99 at Frys and I actually like them very, very much. I am able to store files off my PLEX server that my kids can't view. AKA "Daddy files."
The issue with them is they only store 500GB.This device is discontinued and I wouldn't pay more than the $40 street price for these. However, they are pretty easy to crack open and you can easily replace the built in drive with a larger capacity drive.
I did just that with a 1TB Western Digital 2.5" blue drive.
The drive I replaced it with appears to be thicker. Possibly 9.5 mm height and the built in one may be 7.5 mm tall. With some work, I was able to manage the swap. I was concerned that Hitachi (who now owns G-Tech) may have added some special firmware that locks their devices to their own drives but that was not the case. I just attached the drive and formatted it as normal. Once booted, I was able to see it in the network.
Voila. 1TB available. These make good TimeMachine remote backups. $40 for the G-Connect and $60 for a 1TB 2.5" drive.