I’m not a big fan of the bullet-hose secondaries and haven’t used them much after max ranking them, so take anything I say with a grain of salt.
From what I’ve heard, AkSomati (together with AkStiletto Prime) are among the most viable, so they’re not a bad choice. Regarding the ammo shortage, have you tried them with a Pistol Ammo Mutation mod? You can get it from rotation C in Survivals and Excavations (so every 20 minutes/four excavators), and Baro -the Void Trader guy who visits a Relay every two weeks- also offers a Primed variant from time to time.
Also, if you want to counter the increased fire rate from Lethal Torrent without giving up on multishot, you can use Creeping Bullseye. That’s one of the ‘corrupted mods’ that you get randomly after finding and opening an Orokin Vault in any of the Orokin Derelict missions except Defense and Assassination (info).
Lastly, and least useful, there’s also the Pistol Scavenger aura mod (obtainable through random alerts) which increases the amount of pistol ammo you get from pistol ammo drops, but I wouldn’t recommend going with this since there’re much more useful aura mods that you’ll want to use instead.
I’ve pointed where you can get all of these mods in case you prefer to get this stuff yourself, but I’m sure you can ask in Clan chat for people willing to hand you over some duplicates, myself included.