My solution is to make my own, with plastic DVD racks from Ikea and B4 sized plastic cases from Daiso, a little assembly produces an inexpensive solution for my normal fountain pens.
The DVD racks in question look like this:
Sadly they were out of stock the last time I visited Ikea, hopefully they will bring them back. The B4 Daiso plastic cases look like this:
Using a box cutter, I cut out a piece of the DVD rack to fit inside the Daiso case, the end result looks like this:
This design is meant as a static storage solution, not as a means to carry pens around. One of the drawbacks I've heard from others using the DVD rack this way, is that the spacing between the dividers is to narrow for fat pens like the Jinhao 159.
Some variations to think about are sponge strips to prevent the pens from bumping into the top or bottom of the case, strips across the rack to prevent rattling, velvet lining to provide better protection, etc, make your own and post photos in the comments!