Another vote for supergrit, and the Rhynowet in particular:
http://www.supergrit.com/products/RedlineRedFlexSheets
I've found that the Rhynotwet doesn't seem to last longer, per say, but it does cut well significantly longer, if that makes any sense. With most other brands it seems like cut performance goes down evenly with time, with the rhynowet it cuts the same right up until it doesn't. Its pretty awesome stuff.
As far as finding below 220 grit, I can't say I've ever looked. My stuff all comes off the grinder at at least 220 grit, anything under that I consider stock removal and not polishing. Most of the shaping methods I van think of should leave a good surface to start with 220 on, I.e belt sander/grinder, draw filing and the like