I purchased a PCB holder and it had a max width of 9". That was too short for a project I'm working on, so I made this modular span replacement.
The pieces are 30mm x 15mm x 120mm with an additional 10mm for the plug ends. There is only mechanical friction holding them together, so I would suggest cyanoacrylate glue or epoxy once you have the length you need.
The board I have is about 11", so I printed one male end cap, one female end cap and two spans.
Holder like this: https://www.amazon.com/DEVMO-Adjustable-Soldering-Assembly-Rotation/dp/B08FR12PWX
The author marked this model as their own original creation.