Installing second hard drive on Dell Inspiron 530S (Slimline)

Hi, I'm thinking of installing a second hard drive on my Dell Inspiron 530S. I have noted that there are four unique screws for the existing hard drive, and was wondering where I could get them for my second hard drive in order for me to be able to install the second drive within the case. These screws go into the side of the hard drive which is then slotted into a cage, so the head needs to be the right diameter and height.

I found this image in an earlier post, and it looks like this:

In many posts, it is said that the part I want is Dell Part #WN322, but according to the listing, it is a hex-head screw, and this is clearly a very thick round headed screw instead --> http://accessories.dell.com/sna/productdetail.aspx?c=ca&l=en&s=fed&sku=wn322

In other posts, it was said that an alternative are these screws, but they are also hex-head --> http://www.maplin.co.uk/hard-drive-screw-x-50-37635

Is it just that the hex-head mounting screws will also work??? I'm quite confused right now as to what four screws I need. Thanks for any help.