I've been spending a lot of time on Utahmountainbiking.com's first aid page since they have in depth coverage on treating various outdoors injuries (rekindling my obsessing on this topic since I last built a kit using this site).

The doctor guy there promotes woundcareshop.com and they've appear to have everything from 1-1/4" prep pads to gallon jugs of povidone iodine. You and your friends can have a betadine party <img src="/images/graemlins/grin.gif" alt="" />

Other than that single-use Betadine/Povidone iodine packs will show up in your better first aid kits, the AMK wound closure kit comes with a small tube of Betadine a little bigger than a fast food ketchup packet and I've found wipes in at least one other kit. Other than that you're not likely to find single use Betadine at your corner pharmacy.

And the other means of application I have seen (pre moistened prep pads or sterile gauze pads soaked in it) usually seem to be sterile. This is what raises concers for me.

P.S. The mountain biking site is a really good resource actually even if you never bike because he covers a lot of common injuries and the best way to treat them in the field. There are also lots of good pics of the treatment of injuries of unfortunate bikers so you can see what it looks like when you run a finger through the spokes of a derailer..

wound prep stuff
http://woundcareshop.safeshopper.com/323/cat323.htm?468

utah mountain biking first aid page (in case you're interested)
http://www.utahmountainbiking.com/firstaid/index.htm