how to make a carrying case.

[Fins]

An alternative is:
Husky Aluminum Tool Case

I use a second hand photographer's case...





... bought for $5 at a consignment shop.

As for adding a strap I'd think you could bolt on some small triangle clamps and use any old strap with hooks/clasps. Lost my travel hanging bag shoulder strap recently and had to use one off an old duffle bag... not pleasing to the eye but worked great.

- Fins