Does anyone (commercially) make a 158 Gr 9mm sub sonic hollowpoint?
Fiocchi range dynamics 158 gr 9mm sub sonic fmg are stupid quiet out of my AR9 pistol and form 1 can.
Would like to have some self defense rounds for home use.

Federal HST Micro 150gr 9mm

147gr is the most common heavy grain and like mentioned above the 150gr Fed but I believe that load is actually optimized for shorter barrel pistols.

147gr is natively subsonic out of pistols. How long is your AR9?

4" barrel length.
I've tried 147 grain subs as well as the 158 grain and
I can't tell much difference in "loudness" by ear, though the 158 grain had a different "softer" tone to it.

This is likely due to the burn rate of the powder used.   147gr JHP is often a defense round and higher velocity is desired.  Powder selection alone can make a 200+ FPS difference in 9mm, but the faster stuff will be louder.

Most 158gr is designed for suppressed use, and are loaded with a JHP not for terminal performance but for not having an exposed lead base, for reduced leading if the suppressor as well as reduced lead exposure shooting indoors.  These will likely be loaded with smaller charges of fast burning powder which is inherently more quiet.

This may be a case where you will need to choose terminal performance over sound if you are unwilling to undertake the task of reloading your own.