Anybody can tell where I can get / which model bike fork sliders and single sided swingarm spindle sliders fit the nc 30.
Likewise, are there any reasonable alternatives to R&G frame sliders?

I think you can (or used to be able to) get the fork sliders from Uk ebay, as for the rear any generic fork slider will work as its only a threaded bar, a couple of bungs, 2 washers and some lock nuts, but you lose the ability to use a rear paddock stand. Unfortunately the R&Gs ae just about the best ones available without cutting the bodywork, if you don't mind cutting bodywork then the likes of Ses would be able to help. Hope this helps.