Quantity   Component name
1 × LM324 quad Op-Amp (or equivalent op-amps/comparators) You need four op-amps or comparators to make this work, but as long as they work on the desired input voltages and frequencies, you don't have to be too picky. I recommend using a quad-package IC just for the simplicity of having one shared set of vcc/GND pins and not worrying about differing frequency responses/slew rates/etc.
2 × Inductors should be roughly the same inductance unless you feel like doing a lot of extra math. You can wind your own around a set of washers or nuts in a pinch
1 × breadboard Solderless breadboard, etched PCB, actual board for slicing bread with wire-wrapped terminals, I ain't gonna judge.
1 × Power source Batteries, solar panels, Stirling generator, whatever, just make sure that it's at least one volt more than the total voltage drop of your switching circuit, and has enough current to drive whatever you're trying to power. Please exercise due caution if using high-power sources like wall outlets -- should you electrocute/explode/poison/irradiate yourself, I offer the exclusive service of limiting my "pointing and laughing" session to five minutes or the duration of your eulogy, whichever is longer.
2 × NPN small-signal transistors 2n2222 or similar variants, whatever you have on hand (these can be power transistors, but I'd avoid that just because of the extra space needed -- these transistors only need to carry a few milliamps). Try to use the same variety to avoid wonky behavior from the multivibrator circuit, but it should be fairly tolerant.
2 × NPN power transistors/N-Channel MOSFETs with pull-down resistors Rated to handle at least double your maximum output voltage and current.
2 × Schottky/fast recovery diodes *OR* PNP power transistors/P-channel MOSFETs with pull-up resistors Schottky diodes are by far simpler to integrate into this setup, but you can get a little bit of an output power boost by using P-channel/PNP transistors set to turn on when the N-channel transistor turns off, since their voltage drop will be lower.
3 × Electrolytic capacitors Smoothing capacitors for the input and both outputs. Note that larger capacitors on the outputs will tolerate sudden power draws better, but will result in slower response from the voltage output.
4 × Potentiometers or fixed voltage-divider pair resistors Pots for variable voltages and ripple controls, voltage-divider pairs for fixed outputs.
1 × 1.2v Zener Diode, *OR* a diode with a known voltage drop, with a current limiting resistoor Used to provide a stable reference voltage. Current-limiting resistor is very important unless you love that "roast diode" smell in your lab.
1 × Pile o' Resistors You'll need many resistors of many values; calculations below.
1 × Pile o' Capacitors See "Pile o' Resistors" note