I purchased a premade Common mode choke from Radio Stuff so created a case to protect it from damage when in my rucksack. The case required cut outs to accomodate the coax. The lid then clamps down on the coax to lock in place. These proved tricky and I ended up snapping one but it still works great. Printed 30%, Used 3mm wood screws to hold lid on.
BNC-BNC Common Mode Choke Line Isolator Core Type: Type 43 80-10m
https://www.radio-stuff.com/product-page/basic-common-mode-choke-line-isolator
Hope it helps someone
The author marked this model as their own original creation.