Original using NPN Germanium Transistors.
And here's a layout that's a touch larger, but includes an onboard inverter to give you the ability to daisy chain it.
Suggested hfe for the transistors is between 90-120hfe. The trimmer is used to set the collector voltage. Suggested between 3-5V, with a lower voltage giving a dirtier boost. You can replace it with an offboard pot to allow for on the fly adjusting, like the layout below.