Off the shelf?
There are few options. Induction heating below 1kW is not useful, so I don't know of any real products. There is a wand type device for automotive purposes
http://www.theinductor.com/ but it's above 1kW, and I think near or above $1000, too.
Your only other choice is to build it yourself, or buy one of those silly toy circuits. Same thing, really, as a proper induction heater circuit needs frequency tracking, control and feedback, and protection circuits, and those take time. Anything you'd throw together would be just a toy. (So, hey, if you have the parts on hand, you might as well make something basic, instead of waiting for delivery.)
The other problem is frequency. A few mm graphite rod probably won't heat very quickly for frequencies under 100kHz. Most toys aren't intended to run that fast. So you'll probably be building it yourself, but also having trouble dealing with stray inductance, burning transistors, etc...
For power control, you'd probably just vary the supply voltage/current into one of these things, yeah.
Tim