I like 12V because it opens up car and motorcycle lighting options. Trailer lights come in a great, 2" round flat LED array in multiple colors, but you wouldn't be able to fit a big enough battery pack for it inside the light. For smaller power lights, you could probably use a bike taillight and remove the red lens as they usually have clear LEDs inside. You'd just need to find a good form factor and round ones are difficult to find.
Another option for the switch—though one that would take up more space—is to use a relay for the lights and just use the switch as the switching circuit, so you could use anything. It may be overkill to worry too much about the switch if you're using a small, low power LEDs, but I like to play it cautious.
Also, do you just have one power or do you want to do high and low power lights? I have high and low beams on my USAAF bike, so I needed a 3-pin switch, NC—NO—NC (Normally Closed—Normally Open—Normally Closed, referring to the circuits). Toggle up closes the high beam circuit, middle is off, toggle down closes the low beam circuit. If you just have one level of lighting, you won't need the extra position. There are a lot of options for types as well as style. You want to look up switch types, which you could probably find an explainer of different types if you search "SPST switch" (Single Position, Single Throw, which would be a simple single-circuit on/off switch. The one I referenced for my bike is a SPDT—Single Position, Dual Throw as it switches power between two circuits.). Don't know if that helps or makes it worse.
