Not a manufacturer as such, David builds 0 gauge models from scratch, using whatever materials come to hand. David deserves an entry on this site, not because he mass produces (he doesn't), but purely for his skill in creating 0 and larger models. Two of David's well known models are a Bennie Railplane and Metro Monorail. See both on this Youtube link :
David has also built, from brass, a three rail 0 gauge model of the British Stirling Single locomotive. Details available in Tinplate Times.