If you're looking for a smaller CD for a personal kit - and as much as I like USB keychain drives, CD-ROM's are waterproof and can be read on any system without needing drivers or access to the back of the computer, as is the case with Windows 98 for the former and many systems I encounter day-to-day for the latter.

Round Mini CD-R on Quill.com:
http://tinyurl.com/yukuf