If you look at the Moka's Product page here:
Some users have uploaded their own photos if scroll down near the bottom of the page.
There are some pictures there that have the Moka, Ella, and Gigi all next to each other and they were really helpful to me when I was trying to figure the same thing out.
The shapes are all pretty similar but they do vary a bit. Gigi has a smaller and shallower curve.
The Moka is close to the same size as Ella, but Gigi is smaller than both of them.