The Zune uses standard file formats like WMA, MP3, AAC, JPEG, WMV, MPEG-4, H.264 media playback, so this is easily available from a whole raft of vendors. Check the tools list at videohelp for conversion software, both free and pay.
My eyesight is too poor to use these devices. I much prefer using something I can can watch video on that I don't have to squint.....