I finally found the button I want! I spotted this button on the side of a bin lorry of all places…I found out, via the wonder of google, the make of the buttons they use on said bin lorries and then through the wonder of ebay, found this particular button for £20 inc. postage…billy bargain! Its perfect, its just the right size inside to fit my arduino and GPRS boards in…just needs a bit of hacking to remove the original internals.