Welcome to the forum gerspachd! I have a small knife holder that has a flap that secures the mag. This works well for me as I can carry the mag. in a horizontal position. I found it in my junk box. Denny
I use a Buck Knife nylon sheath/pouch with a flap over the top to carry my spare mag. While my LCP is concealed in its Bear Creek wallet holster the knife sheath is out in the open and available carried on my belt. The spare mag fits like a charm and is easy to access should I need it. Although my knife rides in my right hand pocket no one has asked why I have the knife sheath on my left.