You may want to disassemble the breech block assembly and make sure especially to clean out the extractor cut out as the extractor spring can get jammed up with crud. You can easily push out the extractor pin and remove the extractor and spring for a good cleaning. I find that a lot of functioning problems with Lugers stem from the lack of proper complete cleaning. There is plenty of information available to totally strip down and reassemble Luger pistols.
IMA-USA has good quality repro holsters. You should also pick up a good quality loading and take down tool. It'll make loading the magazine easier.
Original Luger stocks are expensive and tough to find. While there are repros available for sale they aren't legal to attach unless you register the pistol & stock set as an Short Barreled Rifle with BATFE. The C&R list exception for stocked pistols sets requires the use of original stocks with the pistols.
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