Available commercial spectrographs
We're not even going to consider the eBay "specials" advertised as Gem "Direct Vision" spectroscopes....the prism versions are of very limited use to the amateur (other than as a source of Amici prims!!) There is/was one notable exception to the "Direct Vision" and that was the GOTO DV instrument.
Every year the list of active spectrograph suppliers seems to get shorter and shorter.............
For the amateur wishing to purchase a slit spectrograph they currently have the choice between the instruments supplied by Shelyak (France) or Baader (Germany).
Over the years Shelyak Instruments has gone from strength to strength. From their initial offering of the commercial version of the HiResIII Littrow (2005), it has continued to expanded it's range to include the ALPY and LISA spectrographs. (as well as the more sophisticated - and expensive echelle eShel instrument.)
The DADOS, since it's launch in 2008 by Baader Planetarium has remained in constant demand and hasn't changed much. The original 200 l/mm and 900 l/mm gratings were recently augmented by a 1200 l/mm option to increase the resolution (R=5000). They also supply an echelle instrument the BRACHES.