GW still sells Gretchen figs (though they look very different from the pic above). On the site click the Warhammer 40000 button and then a list of armies should pop up on the side, click the button for orks and look around, they sell a box of 10 for not that much.
On the fantasy side look for Grots, you can get a box of 20 for about $35. They are multi part models and should be pretty easy to convert.