Years ago, I was doing ultralight backpacking and thought it would be wise to incorporate an ultralight fishing kit into my setup. I found out about Zimmerbuilt through a friend of mine so I purchased a Zimmerbuilt Tenkara Strap Pack. This was designed for Tenkara fishing but I thought it would work really well for what I had in mind. It stays in my vehicle since I tend to stop at ponds and creeks a lot so I wanted something small yet handy.
This Strap Pack has quite a few mounting options. It was obviously intended to be worn on a backpack of some sort, but I just use the lanyard it came with and just sling it over my shoulder. It works perfectly for my intended purpose and is highly functional.
Here is a link to his site: (no affiliation)