I'd check on amazon. 

I think there is another way to do it too.  You can use thin sheets of wood...like less than 1/8....and you can coat the sides with glue, then clamp it into a form.  This is how eames chairs are made.  They don't bend flat plywood....they buy veneer sheets and glue them together.  This method retains the stregnth of the wood...IKEA has some popular chairs made this way.

Bending/forming wood can be extremely complex... here are some links that may provide you with more info than you'd like:

 http://www.woodweb.com/knowledge_base/Rx_For_Bending_Wood.html

http://www.woodweb.com/knowledge_base/Vacuum_Veneered_Drawer_Faces.html 

The articles may not contain exactly what you're looking for, but they have some pretty good info about the basics of bending/forming wood.  You might also find yourself getting lost in some of the other forums.

Good luck.

Here is a great book to learn more if you are interested.  As well as a cool looking book to have on your shelf. 

http://www.amazon.com/Bent-Ply-Dung-Ngo/dp/1568984057/sr=8-1/qid=1169839395/ref=pd_bbs_sr_1/103-3380272-2260628?ie=UTF8&s=books

You have a few options.

You can kerf your own boards, bend the board, and nail it to an underlying structure.

You can buy pre-kerfed MDF, bend it and nail it, or put a veneer on it to hold it's shape.

You can build up layers of thinner wood that will bend easily and use a form.  You cut thin strip, about 1/8" to 1/4" inch depending on the amount of bend, glue the pieces, clamp them to a form and let it dry.  When it dries, you will have your wood in whatever shape you want.  Check out the "Woodworks" section of the DIY TV network.  The guy does this quite a bit.

You can use steam to bend pieces, but you can't do very large pieces with it.  Only good for long, thin, straight pieces that you want to bend, like a stair railing.

Or, you can buy bendable plywood.  It has the plys running all in one direction and will bend easily.  Sometimes it's called "wiggle wood" and comes in 3/8" thickness.  Only problem is that you need a way for it to keep its shape.  You can either nail it to an underlying structure, or, you can put it in the shape you want, veneer over it, and have it held in the shape you want.  Then, take it out and the veneer should hold everything in place.

I've asked a local cabinet maker how this is done after trying (and breaking) to bend some 3mm MDF manually and he handed me some oddment he had lying around of exactly the kerfed MDF that wayfarer describes. 

It really depends on what and where - bending an 8x4 sheet of plywood in half is rather different from making a shaped candle holder.

If there's to be a blind side to the finished article, try kerfing it - narrow parallel grooves across the part to be bent (1/2 to 2/3 the depth).  Hard to do by hand, you'll need a router or circular saw.

You can also buy ready-kerfed flexible mdf these days - not exactly plywood, but with the right covering...

If you're really feeling adventurous, lamination is a possibility - thin sheets glued together, bent and clamped on a former before the glue dries.  In essence, making your own plywood.

Patience and prior practice needed in every case though.  Do ask again if you decide on a project.