Big (really big) thread on MarsAqua LEDs here - and lots of references to suitable Epistar 3W LEDs. I've changed out a large portion of my array to include a number of 405-410nm, 415-420, and a few select others - as many others have done. There are also a number of videos on how to unsolder the old ones and solder in the new ones on that thread.
This is a fun hobby...
Cheers,
Ray