and if I could add
if you do use a manufatured screen top, I'd suggest weighing it down with a book or something. In my early days I had a bad time with hatchlings and pet store lids. They may be better now, but I still hear stories often from folks who buy my hatchlings.
I'm no metric guy, being an American, (and a Southerner at that) but the dimensions for a ten gallon tank are AROUND 20 x 10 inches. I'm pretty sure about the width being ten inches. And there really isn't a cage "too big". Understand that these animals have the whole great outdoors in their natural habitat. The only benefit to a smaller enclosure is assurance they find their food readily, as evidenced by the deli cup feeding method being so successful.