J, Home Depot sells stainless in a small short roll that is inexpensive (in the roofing section). I think they are even avilable in 15" widths. I found the best way to achieve a straight bend is by scoring it with a blunt knife (butter knife), or a light cut with a cutter. Fold slightly, and use a wood ruler to complete the fold. Stuff the ends of the accordian with crumpled foil to "block" it.
To achieve more of a "round" shape, you can prob use two 2x4s set like an inch apart, drape 2 layers of foil in the middle, press with a chopstick in the middle depression to desired depth. I doubt 300° is going to be a problem. I bake steak in the oven at 500° all the time..
If you want no work at all, take a baking pan that's at least 15" in length, and prop one edge with a phonebook. The low edge will form the "V" that you require...
Remember, molten sugar will burn exposed skin
*snap!* just like that! * Be careful J!!