I've been searching around for a good sale (which I know won't come for a month or two), but nowhere online seems to sell the NS SL-R.
Evogear has some (at least in the outlet... I think the store does as well).
Also, NeverSummer boards usually don't drop in price nearly as much as other boards do. I wouldn't get your hopes up for a super cheap NS board.
All the good NS boards in good sizes tend to sell out. They're one of the few companies these days that can claim that, so basically if you see a good deal, jump on it. Or just buy one now b/c they won't be around later.