Dockers Mobile Pant: The inside vault pocket holds a folder just as well as an outside pocket in my experience, and keeps the clip hidden. Meanwhile the knee pockets fit a PSK perfectly. These now come in microfiber as well as the original cotton.

ScottEvest: should work well, but looks terrible.

This: http://www.magills.com/pgroup_details.php?pgroupid=364

Start wearing a Sport Coat or a suit. Nobody's going to look in your jacket inside pockets. I have two suits from Kilgour French Stanbury with specially made pockets for my knives.

Better yet, just use a postcard. clip the knife to it lengthwise and put it in the pocket. Not only does it keep the knife in place ready for use, it keeps it from printing through the pocket.