I have seen more interest in the CF-73 pop up here lately. I have several units I was going to upgrade my kids too from the CF-28 Mk2/Mk3 they were using. My main deciding point was ATI 9000 video card that was available on the CF-73N/Q (Mk3) model. After getting a few units I did a big DOH! the caddy was very hard to find and expensive. This is what I came up with after doing some brain storming. I have done one previously but ordered enough stuff to do more, just didn't get around to it yet so I decided I would do one more and do pictures.
You will need.
Gel pack/ protector / silicone case (what ever you want to call it)http://www.ebay.com/itm/3-5-Silicone-HDD-Hard-Drive-Skin-Case-and-Protector-/150732434496?pt=PCC_Drives_Storage_Internal&hash=item23185a6c40
Remove the two screws holding the handle on. That will allow you to remove the palm rest cover on this model allowing you easier access to guide the caddy cable and harddrive into this model.
Now install the cable onto the harddrive, then slide the protector sleeve on to the harddrive. It has large bumps on all 4 corners. You will need to trim the two ends down nearly flat on the end where the caddy goes for it to slide in correctly.
Pushing the caddy in you will have to stop some and shove the harddrive back into the sleeve some ever so often. The bumps on the end will help hold it into place, it is a very tight fit and won't just fall out.
Enjoy your CF-73!