Short answer is, practically, no. Micarta, G-10, and the like would be far too stiff. In principle, I suppose you could grind two clamshell halves thin enough to give; but keep in mind that these laminates need to be stock-removed into shape, not molded. You would need to start with a VERY big piece of micarta, then whittle away, and on the interior side completely by hand for a very, very long time. A customized piece would probably cost you more than any gun you'd holster in it, and in the end it would probably rapidly wear away at any finish and be functionally less effective than kydex, wet-formed and beeswaxed leather (or leather treated with Obenaufs), etc.
