
When I was doing idustrial ultrasonic inspection I had a fitted case made up by my partner out of foam covered in dipping rubber that fit exactly the transducers and wedges for angle beam inspection. The added benefit is that you knew exactly what was missing at the end of the job.
I am by nature not a neat person and cram it and jam it fits the usual way I store things. Blow molded cases tend to have a lot of waste space and space is limited, so far I have used a flexible canvas bag but the mess is incredible and things get lost (I swear things crawl out).
With a few exceptions trailer tools stay with the trailer, the only exception is the clamp meter and some of the electrical things i.e. additional Power Pole connectors.