Homemade ice pack made by any gel type material should work.
These type of ice cubes are easily available in the market. They are also an alternative:
As of now I am using dish washing liquid put in ziplock bag and keep this in freezer. It did work well.
I then made a sponge ice pack to keep on top of the container which will keep the things cool from top as well.
I did try this last week.
Once I find correct size and combination of items I will improvise on this.
More experiments next week.