If you're looking to buy one, I can't think of anyone that is building them right now.
If you're looking to build one...
As long as the front grip is not perpendicular to the barrel, it's legal. If it has a pistol grip for the front grip it's classified as an AOW (Any Other Weapon) and falls under NFA restrictions.
Lots of discussion on a couple other boards about using AMD-65 kits to build a pistol. A standard upper gas tube is easily converted to work on the shorter AMD gas system. Just cut the standard tube to length and use a 3/8" socket extension to reflare the end of the tube. You may need to use a round form and hammer to fine tune the shape, but it's an easy project. The Rear Block is replaced with one that cannot accept a stock. K-Var sells one that has a sling swivel mounted on it.
K-Var also sells a receiver/barrel stub from an AK-74. The barrel is about 9.5" long, and is just about the limit if using regular handguards. K-Var also sells a combo gas/sight block that will work with the barrel stub if you use a Krinkov gas tube. You can use the Krink gas block, but if you use the Krink gas tube, you will have to use the Krink Handguard Retainer and lower handguard. There isn't enough space to use a standard HG retainer if you use the short Krink gas tube and gas block.
Just make sure to use a virgin receiver when making a pistol. This can be accomplished by having the FFL transfer agent log the receiver in as a pistol receiver.
Before you build, make sure there are no state laws with pistol restrictions where you live.