Here's one click here, but expensive at £33 +PP, & can only hold one IDE drive at a time.
If you have spare internal HDD mounts in your present PC, why don't you install them inside the case?
Another option, if you have two spare 3.5" external bays, is to get couple of these click here. They fit flush into a 3.5"/optical drive bay, so nothing sticks out. You'll cry if you see the price of an equivalent SATA one click here. You may find the IDE ones cheaper elsewhere though - try Amazon or eBay. G