I keep a Doug Ritter PSK in my life jacket spare radio pouch and it has stayed sealed up perfectly.
I have two radio pouches, the first has the aforementioned PSK and the other is empty for when I actually carry a radio. I carry a 55gal and 2 35gal trashbags in one pocket and a pair of leather gloves in the other pocket. I also hang an 8" Crescent wrench, hard hat, red blinker light, and an LED flashlight on my life jacket. I do carry some other things in the pockets and pouches such as spare batteries, small flashlight, etc as well.
The radio pouches are Int Orange and run $5o-$75 each. I wouldn't pay that but I have them because my company has issued them. An M-16 or AK magazine pouch will hold a PSK nust fine and run in the $5 range. ALICE clips on a mag pouch makes the pouch easily attachable to most life vests.
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QMC, USCG (Ret)
The best luck is what you make yourself!