I hope this doesn't sound too flippant, but I suggest you drop iodine completely. There are better ways, like boiling.

My bible for stuff like this is James Wilkerson's [/i]Medicine for Mountaineering[i], sixth edition. His discussion of the caveats, conditions, and contraindications of iodine and tincture of iodine takes up nearly two pages. Total disinfection requires more time than would be required for boiling, in addition to something to counteract the iodine taste (after allowing time for the temperature dependent process to work). He does state that tincture of Io would be useful in a major disaster where boiling might not be practicable.

I was interest to see, reading the section on iodine usage, that my sealed bottles of PotableAqua, carefully resting in my supplies, had now passed their best buy date (more than four years old) and were now undependable.

Personally, I have used boiling as my primary technique for many years in many situations involving clearly polluted water with no ill effects whatever. One of these episodes lasted for an entire month.

Wilkerson notes that the CDC and EPA recommend boiling for one minute. In his judgment (and my experience )bringing the water to a boil is adequate. Boiling temperature varies with altitude, but even on the summit of Everest, water boils at 165F, the temperature at which milk is pasteurized.

To actually answer your question, you can find dropper mechanisms with a rubber bulb and glass tube which you could carry separately, but, frankly, that is getting a simple process rather complicated. A lot of folks go to filtration these days, and it seems to work,but you are hauling around an extra bit of gear....