One of my projects (AVR DDS 2.0) requires multiple power supply that could supply +12V, -12V and 5V. Back then, I have constructed a simple transformer-based power source with few linear voltage regulators. It works fine but is powered from mains 220V which is not the safest solution to squeeze in to box enclosure. Another option was using ATX PC power supply, but it is too big. Banggood has been offering pretty attractive power supply kit which has a voltage boost circuit which rises voltage level either from USB or from the 5-24V jack. Power supply kit has most of the voltages that you may need including + 12V, -12V, + 5V, -5V, and +3.3V. It is capable to output 300mA per channel. Total power is limited to 10W which is not bad and can provide a short-term high current single output, but be sure to attach included heat sinks to protect ICs from overheating. It is advised to keep output currents of each channel to less than 0.2A.