AFAIK, all commercial emulsions are normal contrast for printing paper use.
You may have to make your own. A simple AgBr/I emulsion is probably sensitive enough at that wavelength, but there are dyes that will sensitize this better. There is a web site for making laser emulsions.
I would like to find a very high (graphic arts) contrast emulsion
which I can coat onto glass plates. Plates are approximately
18" square. I'll be exposing to 488nm (blue-green) light from a
laser. I want to try to achieve Dmax of 4.0 or better.