I think you're being misled by the height of the spike at the blue end, versus the (lack of) width. And if you had a powerful need to fill that gap around 480nm, they make LEDs around that color, called "blue" (470nm center) and "cyan" (505nm), so you could mix 5 (cool, neutral, warm, blue, cyan) and get pretty good coverage. In particular, Luxeon Rebel, Blue, bin codes 4 and 5 -- 475-480 and 480-485. This is really, truly, not an insurmountable problem, if you really want quality.
Fluorescent bulbs, even high-quality ones (see below) have the problem that their basic light is not just "around" particular frequencies, it *IS* a small set of particular frequencies. You can see this with a diffraction grating: http://dr2chase.wordpress.com/2008/05/08/spectrum-led-vs-fluorescent/ Interestingly, you can see the 480nm dropout in the LED spectrum (narrower part of the smear) and you can get a feel for what color that is -- truly, blue-cyan.
I am a little curious whether it would be possible to make a two-part "white" LED for diffuse light; have a separate glass with phosphors on it, and illuminate that with royal blue.