The .22LR HK/Umarex MP5s come with the collapsible stock, so there aren't likely to be too many "take-offs" around unless someone bought the aftermarket fixed stock to replace the one that came with it and then didn't like it. Real HK94/MP5 stocks won't fit on the Umarex guns, so you can't use a "take-off" from a full caliber gun. HKParts has the Umarex fixed stock, last I looked.