I'm pretty sure he is just referring to a standard quill stem where the stem bar (from bolt to handlebars) is flat horizontally. Usually referred to as -17 degree (or 73 degree) I believe. What he is looking for would be 0 degree (or 90 degree). In addition to what others have recommended, Salsa made some 0 degree stems; my Trek commuter bike has one on it (brother built it from his parts bin).