The Saiga lacks a lower handguard retainer.
You can press off the FSB and gas block and install one (and then press everything back on.)
Another option is to make or buy a clamp on lower handguard retainer.
Dinzag over at the Saiga-12 forum sells them.
I made this one using a two piece clamping collar and a hacked up Romy retainer..
The cheap and easy way to add a forward pistol grip would be to keep your stock Saiga handguard, cut a hole in it, and attach a pistol grip using a standard AK pistol grip nut and screw.
These pics show a 308 handguard that I did that to.
I also shaved the handguard down with a belt sander and cut some notches in it to match the East German upper handguard.
Rail is hacked out of a lame B-square AK scope mount.
Sling thing is hacked from a scope ring.