Your HDD options aren't limited to actual mechanical or Solid State drives? You can also have a CF or Compact Flash vintage memory storage device emulate an ATA drive, in fact, there's a SATA adapter allowing mounting of TWO CF cards of any size where they could combine for the total size you require. Also prices on 128GB flash are VERY affordable now. There is also the option of microSATA adapting PCI Express capable SSD type drives, these mount just like mSATA Wireless cards, and look like them, as do various versions of tuner cards using the mSATA connectors. There are a few companies offering mSATA SSD drives to mount to a standard SATA adapter for laptops and even desktops, one of their great advantages is capability to mount in a notebook or desktop PC.
In recent years a lot of these mating capabilities come by way of Chinese made electronic adapters, a logic board and circuit mated to connectors allowing two differing devices to connect where they couldn't before!