Where's a good, safe place to find RibbonX icons for MS Office applications?

Now that I’ve finally figured out enough XML and VBA code to put together a ribbon in Excel 2007, I’m looking for some icons, as MS’s own offerings are rather samey and mostly geared specifically to Office applications.

There are dozens of sites with free icon sets out there, but obviously I don’t want to download from a site which is going to load up the work computers with tons of malware and crapware. Any Dopers with experience in this? Also, in a related question, how difficult is it for a someone without graphic design experience to build their own icons in the Office graphic editors?