I've also ordered Grishko unitards through Dancechoice.com.  I received the "polyamide" clothing in size large (I agree, the customer service via email was very good).  While the fit was okay (a larger man could still very comfortably fit into the large), I don't believe the material they claim is "polyamide" is actually polyamide.  I know what polyamide weaves are like and the Grishko material looks, feels, and weighs very much like nylon/spandex and is quite a bit heavier weight than milliskin (for comparison).

"Nylon", a brand name of Du Pont (in 1937 they patented a production process), is a polyamide. "Perlon" is more or less the same material, produced in a different way (patent of the former I.G. Farben). There are other polyamides, natural and synthetic.

Thomas