You would need to see the spectra of the various LEDs available and create a mix along with phosphor mixes. The closest thing is something like a BLAIR-CG light engine from aputure where they have something like 9 different colors of LEDs that mix together, but they don't put any infrared leds in them because they are for movies and they don't put any UVB or proper UVA leds. But there are infrared, UVA & UVB LEDs that you could apply the same kind of engineering principle to make something that closely follows the sun spectra.

No, you can't buy them as bulbs. The closest thing is those red light therapy panels that include them.