Spares for a Heatstore night storage heater?

I'm looking for spares for a Heatstore night storage heater, more specifically the asbestos-like tiles which lie on top of the bricks.
I say asbestos-like but I'm hoping they're not asbestos since the old ones crumbled to bits when I had to take the heater off the wall recently to fit skirting behind it.
Please look at this picture to get an idea of what I'm looking for
http://www.derekr.pwp.blueyonder.co.uk/images/tile.jpg
Actual size is 23cm x 12 cm and they are unbelievably fragile - that is the last one out of four which is still in one piece (but ready to break).
Any idea where I could find such a thing? Will the heater be safe to use without them?
Cheers.
--
DerekR,
Edinburgh, Scotland
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Thanks for the link Joe. Now added to the favourites list.
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