I think it is simple to model but with large flat parts like that made from materials that work well outdoors I’ve found they suffer warpage easily, so probably need someone with a really good printer and / or lots of experience.
The sealing is in the lid, they still have a drain.
I have never seen a requirement to have a sealed top lid on a gas bottle locker.
I didn’t say it was a requirement, just that modern ones have seals. I say modern, my 1999 Jeanneau is sealed so it’s not all that recent.
No, as with sealing the lid there are no requirements for gas on a sea going boat. Selling a "gas locker" requires meeting a fire standard, but that's a different question as with the seal on the lid and is why OP was quoted several hundred quid for a fancy box.
On most boats a fire bad enough to get the metal gas cylinder inside a fibreglass locker to explode is already going to have been reason to abandon ship.
Small boat safety scheme chapter 7 worth reading when considering gas bottle alterations.
The actual BSS chapter 7, to which these checks refer, can be found at
Whilst true, I have found that discussing BSS recommendations during an insurance survey quite helpful.
Goes both ways - I had one surveyor wanting me to improve my gas installation, and we discussed elements of BSS which he felt was appropriate and realistic, and another that wanted something that was not on BSS (as it happens, a lid!), and so I managed to talk her out of this.
Then maybe a little redesign is in order (add a hinge and latch).
