Hi Jay,
Have a look around this website and I am sure you will find something the right size.
https://www.carryitcases.com.au/
"Storm" and "Pelican" cases are the best. They are now made by the same company. They are slightly different but both top shelf. I have 2 Storm cases and 3 Pelican Cases. The Pelican Cases are probably a little thicker than the Storm Cases but I prefer the catches on the Storm cases.
By warned, they are expensive. One large enough to hold a HEQ5 Pro will probably cost 40% of the cost of the mount, if not more.
If you hunt around on different websites you will find some cheaper "Asian" knock offs of these that will be a lot cheaper and probably adequate, if your not taking the mount swimming with you.
I had a friend in the USA who had his very expensive eyepiece collection in its Pelican Case washed/blown away by Hurricane Katrina in 2005. His eyepieces were returned to him by a good Samaritan some 10 weeks later all in pristine condition in their Pelican Case, which itself was unmarked. The moral of the story? You usually get what you pay for !
Cheers
John B