Sir Ulrich, one of the guys from SBG put together a pretty comprehensive how-to with good pictures and explanations, give it a shot if you want to build your own, including how to get the curve in it:
http://yeoldegaffers.comHere's where I go to get mine made (as I don't have the space or tools to make my own):
http://www.oakheartarmory.com/store/You can get curved shield blanks for about $25...but they will also paint them to your spec should you desire it. They made my Templar shield- sized and strapped to my spec. As I'm left handed the majority of shields to be had won't suit me, these guys are easy to deal with, communicative and their work is excellent considering the price. That shield of mine actually needed to be modified for a longer guige strap which I had done at last year's MDRF but knowing what I know now, the next shield will be even better. Also, they can wrap the edges for you w/hose if you were so inclined...but as my shields are mostly for show I opted to not include them.
Here's a shot of the shield: