Also known as a magnetic fusion drive, or a mega-ion drive.
A staple of high end sci-fi is the replicator or the nano-assembler. There is a much more practical and less technomagical way to achieve the same goal. The exciting thing is that this technology exists now, and we're getting much better at it.
The PCs are stuck in a town with a strict peace policy, the tiniest scuffle can land you years in prison. The town also happens to be a tourist haven, so inn-prices have skyrocketed. The only way the PCs can rest is if they splurge on a room, with their enemy.