I prefer using a silk pillowcase to the silk bonnet. I not only don't end up with a dented forehead for hours, but also using it is better for skin (moisture isn't leached out, and there's no drag). I get mine from DharmaTrading. NAYY I've paid more for cotton pillowcases at Bed Bath & Beyond, and that wasn't all that recently.

Baby Fine 3B, low porosity, normal density and elasticity
CGing since July 2008