Small self-contained energy source
I am interested in making a energy source similar to iron man's arc reactor in the fact that it is small, self contained, and and powerful. I would like it to be hand-held, but I can deal with slightly larger or even desk size. It needs to be long lasting. I am well aware that an arc reactor is fictional, but I just need something that may be similar. It can be a large project (I have time) but needs to be not super expencive. Around $500 is the max I can go for!
I hope someone can help,