Captain - "Non-slip" and "concealed carry" work against each other. Silly as it may sound, the stock, non-thumbrest plastic grips are the best I've found for concealed carry. If you want something prettier, go for wood in the same shape.
If the grip material grabs your hand, it'll grab whatever you're using as a cover garment too, possibly causing it to rise up and reveal your roscoe. It's worst with a light shirt or t-shirt.
Having a non-sticky grip is also an aid to quick acquisition of your pistol, too, as someone already mentioned.
Regards,
Chuck