I thought it would be useful to come up with a mix ratio for Iodophor for temporary use in a spray bottle. Using the instructions on the bottle for home brewers, the ratio is 1 tsp Iodophor to 1.5 gallons water. I work this out to be a ratio of 1 part Iodophor to 1135.6 parts water. So, since 1 drop of Iodophor is about .05 ml, it will create 56.78 ml sanitizing solution.
So, to create 500 ml of sanitizing solution you would need about 9 drops of iodophor from an eyedropper. Hope this is useful to brewers with Iodophor on hand but not Star San, which seems to be the (logically) preferred choice. Also if my math is off please post a correction.