5V switching regs able to handle the current we need are few and far between. The TI booster boards will do it, but they're pretty expensive. Switching power supplies require (comparatively) large caps and
coils, so you can't make them on a single chip. The circuit isn't terribly complex, but it's just barely out of the realm of something you'd want to DIY (unless you've had some formal EE training).
I know that Hoog (the guy who runs Madvapes) was looking into getting some adjustable boost/buck boards made for a reasonable price, but last I heard, he was having trouble finding an engineer to design it for him.