I can't remember where I saw it, but someone makes an arm holster for your phone with an extra pouch in the back that had a fast release velcro instead of a zipper. It looked like the standard armband phone strap with the clear front, the pouch was big enough for a TCP or LCP sized pistol.
Here's a better link than the NY Post.
https://cowboystatedaily.com/2024/04/06/smiling-man-poses-with-wyoming-wolf-muzzle-taped-shortly-before-it-was-killed/