What sort of control do you plan on using for it. There's super bright white leds around but they need a dedicated driver for them or depending on how the topper is to be built you could possibly use something like the 120led/metre strip and cut and join it to fill in the space. The strip could be modeled as a single pixel or alternately configured like the seizure stars that some people create.
Virtually all the individual leds in nodes or strips are going to be about the same brightness. By going to 120led/metre you can get a lot of leds into a small space.