The icons are not static resources located in a directory. You will have to use the browser to find them and copy them to somewhere.

The easiest way is probably by using Chrome.
1. Launch Chrome.
2. Press F12 to open the Developer Tool.
3. Select the Network tab.
4. Select the Img filter (so that only image resources are shown in the Network tab).
5. Log on RDNG and do whatever needed till you see the icon you want to reuse.
6. Check the Network tab and confirm which resource contains the icon.
7. Open the resource in a new tab.
8. In the new tab, save the image as a local copy.

Note that all CLM applications consolidate a group of icons into a single image. For example, the "rm-type-icons-sprite" image (264x264 in size) contains around 100 icons. So you need to chop them up to get individual pieces.