For light cover garments, you might try a mag pouch from The Wilderness in horitzontal configuration. I have one and it disappears in plain sight. I usually carry two spare mags in a regular leather pouch from Milt Sparks, but sometimes clothing makes that difficult. The little wilderness pouch is excellent for those times when only light cover is appropriate. You can find them at http://thewilderness.com
To bad those come in leather But I try one out anyway. Thanks for the tip.