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As the OP does not live in the USA or associated countries. There are no burst disks on cylinder valves, so the LDS would not be able to supply them. It is the opposite discussion that has happened on here where european cylinders have appeared in the USA, are to european standards, have M25x2 threads and no burst disks.
Let’s skip this silly part given the user and his post history and acknowledge the density of homebrewers and gear modifiers is decent in the US and significantly higher in Europe. There are unfortunately types of bottles only available or imported in some regions. Perhaps this has solved Agro’s hunt for the elusive and magic buoyancy characteristic American 2L!
Yes this is kind of the issue. You can use a machine bolt, or the plug with a SS disk, or 2 copper disks. All of them will eliminate the ability to burst in the typical sense. But they are all subject to corrosion and the weak link between the valve body and the sealing gasket will remain. So none of them truly eliminate the burst disk forever and ever. Every decade or so the OP should remove the sealing unit (whatever type) and replace the gasket.
