Power supplies and transformers that convert dc to ac aren't cheap unless you're using those small wall warts. I wonder how RC batteries would do? Sanyo RC Nicads used to be very popular with RC hobbyists (model electric cars, boats and planes) and took a beating and could CRANK out the amps or power needed. You could charge them also w/a 12v dc cigarette lighter adapter (portable).it needs a power supply that can deliver more current.
the Bud Toaster does 60°F to 380°F in 20 seconds by pulling 12 amps from the A123Systems cells. An AC power supply delivering 12 amps is big and expensive.
PS: Those lithium A123Systems cells look like they'll fit the bill. Funny I saw those after I made this post. Guess we're thinking alike. Well those Nicads may be cheaper and do take a beating. The lithium ions would definitely be in a smaller and lighter package.