Actually, the N-acetyl version (N-acetylcysteine or NAC) is probably
the best form.  As to what company, I don't know.
www.consumerlabs.com is a good place to start, but they have yet to
review NAC.

I use a rather costly form (relatively) from Germany avialable at the
New York Buyers' Club ( www.newyorkbuyersclub.org ). Jarrow also makes
a decent product....basically, if it stinks TOO much like rotten eggs
(NAC is a sulfur-containing amino acid), it is probably too oxidized.
Some smell is common--except with the German type I use.

        George M. Carter