The barrel length of the PA-63 is the same as a Walther PP and is longer than the PPK. As far as leather goes, I have found that anything that fits a PP also fits the PA-63. To avoid any problems, I would choose a holster without a top thumbreak or with a retention system like the Bianchi Minimialist series. I use a Bianchi Minimalist for my PA-63 and it fits fine and is VERY concealable. As far as the kydex or plastic, like a Fobus, I would think the PA-63 should fit. In the case of the Fobus, I believe the bottom of the holster is open so the longer barrel of the PA-63 would just protrude farther than a PPK would. Same goes for leather. If the holster has an open bottom the PA-63 should fit any holster for the PPK. For the money, you cannot beat the Bianchi. It is more concealable and very comfortable and has a little give that the plastic holsters don't have. Plus, because it is softer, I don't think it prints as easily as the plastic with its sharper edges.
Steve
