If they take 3 AAA's you can power them with a 5VDC supply. A 1 amp supply (1000mA) should power 4 of them.
Yeah but that also means having to manually turn each one on and off. Guess it depends on what's more important and/or convenient.Just my two cents worth, but running off batteries would provide a lot more flexibility on placement with no wires to conceal or trip over.