Op amp based DC-DC voltage doubler
If you have a microcontroller (as I suspect) driving your display, you could probably use a spare pin with pwm to drive a simple capacitive voltage doubler. Thus you'd need only common parts (caps, diode, a bjt/mosfet) - no need for 555, opamp or whatever and no inductor so little added noise.

Edit : here is the classic voltage doubler circuit :







simulate this circuit &ndash; Schematic created using CircuitLab

C1 should be much smaller than C2 (lower C1 gives lower ripple, but lower curtent capacity and slower voltage ramp-up), and critically diodes should have lowest possible Vf. You won't get exactly doubling from this circuit as it is, but for what I guess your application is that may not matter much.

Drive PWM pin by setting it to 127, and choose frequency matching C1 (or C1 matching the PWM frequency).