You can but it will be a pain. Ebay is your best chance on finding most of the parts.
To make it a bit easier the CD/DVD drive is the same as the drive used in a slot-load iMac and the CPU is the same from a QuickSilver.
In all for a base system you need the following.
CPU 450/500MHz CPU
PC100/PC133 SDRAM (expandable to 1.5GB)
AGP 2x video card
If you need more info on the cube look here http://www.apple-history.com/body.php?pa...e&order=ASC