No idea about a pistol-grip stock, but if you have the older tube-fed gun you should be able to retrofit a 10/22 stock. The 10/22 was actually designed as a companion to the .44 carbine –– they have the same LOP, sights, etc. The 10/22 Tech Sights will also work on the older .44s, FWIW.
I've got one (the tube fed one) as does everyone at my deer shack. Story from Ruger's gunsmiths (who will still work on one if you send it in) is that they are not a long-lasting design and they were tough to make reliable. Too much variance in ammo, I'd guess, and whiny people who shoot LRN or wadcutters in them and never clean them (they are a pain to field strip and clean). Lead from the bullets will clog the gas ports.
They do wear out (much like the Remington 740-series autos) and when they're dead they're dead. I shoot mine sparingly.
Mine shoots about 4MOA with Hornady LeverEvolution, as long as you wait 5 minutes between shots.