I'm in the camp of most fabrics will not hold air. At least one fellow sewed silk tubes into which he inserted balloons. You could try that, but inflating the balloons each night is a pain and untying the knots is not always successful. I have had some luck in using "flattish" mylar balloons as pillows. I wrap my inflatable pillow in my down sweater and put the whole thing into my pillowcase-stuff sack made from Tyvek. Tyvek gets softer and quieter with use and washing.