Looking over your post, I'm reminded of the Dayhiking Kit I put together using a 2qt canteen pouch that has both ALICE clips and a shoulder strap. That canteen pouch, or the 1Qt canteen pouch now being marketed by Rothco (has ALICE CLIPS and a shoulder strap, along with an external pocket large enough for a smart phone), or M-16 ammo pouch (for 20 or 30 round magazines) could be perfect for carrying a PLB or SPOT on your person for almost any type of outdoors sports be it canoeing, hiking, or climbing, etc.

I use a radio pouch (about the size of an M-16 pouch) to carry my Doug Ritter PSK (thank you Stu) on my life jacket. It also has velcro flaps for belt carry and a shoulder strap as well.

The usual disclaimer applies IRT ROTHCO.