It all depends on your galley layout really. Maybe one of those s/s handrails you can buy from the swindleries will suffice. Without seeing what's needed it's a bit hard to comment further. Any chance of a photo?
A cooker crash guard is seperate from the cooker. On some boats the cooker is receased back in the worktop and the top fiddle of the worktop extends across the cooker opening to form a guard. On other boats it is stainless steel tubing spanning across the cooker opening mounted on the units either side.
At the boat show I saw a number of boats which had the same guard. It was made of rectangular section stainless steel and had built in achorages for the galley strap. Hence I suspect that as it was the same on different makes of boats someone must be producing them.
You should be able to get a piece of stainless strip from a Non Ferrous metals supplier - yellow pages.
I bought some to use for garden railings ( too lazy to paint)
The strip was about 1 1/2 " by 1/8" I think.
You can drill it easily enough at low speed with lubricant.
If you need to bend it just heat it red hot over a gas ring or with a blow torch, put the ned in avice and just bend it. Its not difficult. The problem is in getting two bends in the right place if you nee to.
You will have more of a problem if you bend highly polished stainless but Autosol polish will probably clean it up.
I second a local fabricator - I had one made which was an asymmetric shape, so impossible to get off the shelf. £45 well spent.
Also note that I have seen a lot of mass-produced SS tube products which have been inadequately purged inside before being tig welded - messy hidden welding spatter that will rust.
If you mean something to stop pans and stuff flying off; then I bought one from IKEA which is meant to make your domestic cooker top child proof. It was pretty well made, stainless steel, arrived in bits (flat-pack) and I was easily able to modify it to fit my boat hob. Don't remember cost but it was very cheap.