SunTour Power ratchet shifters are great. They were made in DT, stem, bar, and bar-end mount styles. The stem, bar, and DT versions go for cheap ($10-25) on ebay (the bar-end version goes for a bit more--$25-35).

They're the best non-indexed sifters I've ever used. Yes, people say the [Simplex?] Retrofrictions are better, but I've never used them. ST Powers must be a close #2, if so.