After a bit more searching on Amazon, I found exactly what I was looking for.  For all you out there who need to mount a 3.5" or a 2.5" hard drive in a Dell PowerEdge server, don't pay 400% more than you need to by buying through Dell, just get what you need from Amazon or the like.  The hard drive caddy's I posted here, are $ 16.99 each, said to be compatible with Dell PowerEdge servers, and at the time of this writing had 18, 5-star customer reviews.  
I'm trying to mount two 3.5" hard drives in the front, hot-swappable drive bays of a PowerEdge R710.  I thought the server would have the rails to mount the drives, but it seems I was mistaken.  Can anyone direct me to the part I need to buy, so that I can install a 3.5" drive in the front, hot-swappable drive bay? Here's a picture of the existing drive installed in the server, alongside the new one I just bought.   [IMAGE]   Best regards, Mike
Hardware to mount 3.5" drive into PowerEdge R710