^^^^
The other important thing to keep in mind here, as Charlie noted, is that you don't want too high a concentration. That 99%, or even 90%, will evaporate too quickly to kill bugs, but I suppose that rapid evaporation is a plus when cleaning optics. Given that you don't need or want that level of concentration, there's no need to source laboratory products. The 151 proof Everclear really is a great choice. It is the right concentration, and allegedly safe for human consumption. Certain events in January, 1984 still lead me to question this last point, but that's another matter.