We are accustomed to using charge pumps to produce a higher supply voltage than that provided by a 9vdc supply. The basics of the chip are that it uses an oscillator circuit to produce pulses that are effectively "summed" by a network of diodes and caps, to produce a higher voltage.
But keep in mind that you're starting out with DC (from a battery or adaptor), and then essentially converting it to AC, before reconverting it back to a different DC. What if you start out with AC?
I was trying to organize the files in my "Temp" directory, and re-stumbled onto a scanned page from an old 70's circuits book that provides simple diode/cap circuits for doubling and tripling the supply, while at the same time rectifying AC to DC. In theory, one could take a 9VAC supply (something which I imagine is readily available in the wallwart discard pile at thrift stores, or even available from more and more of the pedalboard power brick units), and double or triple it (minus whatever is lost to the diodes). So if you have a 9VAC source, you could use it to provide a 26VDC supply with just a few parts. And the best part is that you aren't limited with respect to current, as you would be with a charge pump chip.
I have the vague feeling I may have posted this before....but having just stumbled onto it, I'm posting again!