I think the Kent Iodine will more likely be found in the salt water part of your fish store. Home Depot I don’t think will have any thing that’s made for a fish tank but will have some stuff for the ponds. If you can’t find it at your LFS look for a salt water store or ask to see if they will get some in for you.
I think your best bet would be to make an order off the net with the cheaper prices on that type of stuff. Don’t for get your filter pads, test kits, and any other chemicals you use. Most of that stuff is so much cheaper off the net and I get most of my stuff in 2 days if you call in the morning.