Why 460nm specifically over 450nm? Or, why single mode over multimode?
The only commercial single mode 460nm diodes are 50mW and around $500. TopGaN is the manufacturer and they do not produce large scale batches.
450nm diodes and multimode 460nm diodes are far cheaper and more available. It's probably more cost effective to buy the 450's in bulk, bin them by wavelength yourself and just use the high wavelength ones.
Hey you know I saw some on ebay going for a couple hundred for 50 of them. They are early Osram engineering samples with a wavelength of 450-460typ 3.8mm