Help missing key to turn on gas fire

I have a gas fire in my sitting room - and have lost the "key" to turn the gas supply on - it is like a large radiator key - does anyone know where I can get a replacement? The size of the valve that needs turning is approx 10mm x 7mm. My neighbour has a key that fits so I am assuming they are a standard size.
I have been to a fireplace shop and 2 hardware stores but no-one can help me.

 

The mains gas pipe goes into a gas cock, which then leads to the gas connection in the fireplace - which looks like a real coal fire. So need to turn the gas cock tap on to turn the gas on to the fireplace to light it, and then turn off when not in use. It is a Victorian fireplace and appreciate new gas fires probably aren't set up like this anymore! My neighbour has similar set up and they have an old fashioned key, with a brass knob attached to a hollow metal tube - the tube is then flattened into a rectangular shape at the end, which fits into the gas codk to turn the tap on. I need to find a similar tool. Any suggestions please?

 

Thanks for the link - think it might be the right size, will let you know when I receive it. Thanks again.

 

No - 10 years! But thought the key that was on the mantelpiece was the right one. Have had the chimney swept and checked, and the gas checked, but never used the fire until now.

 

out of trim - the keys arrived today (excellent service from BES) and they are the right fitting! So ma very grateful to you for the link. I asked so many plumbers merchants and ironmongers, none of whom were able to help, so thank you very much indeed (and the key was very cheap!)Worth knowing for people in Victorian etc homes where the gas supply to the fireplace is not very sophisticated (but still in working order)