There are several styles of fiberglass shingles that look just like cedar. Some just have shaded areas painted on, whereas others actually have several layers of different shapes to make up a shingle.
Our last home had the layered version, and its staggered look was very convincing. Granted, when you see them up close, like the sample at the home store, they may not look exactly like cedar, but once they are on the roof, it is very hard to tell.
Of course, as the price goes up, so does the reality. I know that the home stores have a decent pattern, but I was in a roofing and siding specialty store, and they had a version that was staggered in both width and length. I think you should be able to find something there you will want to use. Like I said, itís probably more pricey than regular shingles, but still cheaper to buy and install than the real thing.