Jazzman - Your post reminded me that when I first hiked the Tour du Mont Blanc a few years ago I saw a group of Italian hikers and had what looked like some really good shoulder strap pouches. I looked and admired them but I didn't ask the brand, wished I had. When I started to look for them online when I returned home I couldn't find anything which resembled their design so in the end, I gave up.
From memory they were about 8" long and waterproof, worked by zips and looked stylish as well, my observation was that they had been designed to clip on a shoulder strap rather than being permanently fixed.
After giving up on them I bought an OMM chest rucksack which was fine for a while but it had one drawback, it wasn't waterproof.
And as I evolved in what I felt was necessary to take with me when hiking, I gradually lost interest in the idea of of shoulder pouches.
Ive tried a waist strap bag as well but I stopped using it because it was often empty.