http://www.connectstores.com/P.E.D/sp_17781-20.html
but probably cheaper from wholesalers
MEM do a better item specifically designed for the job and used by some DNOs. I cannot find the exact reference number but it starts MEBAN2EBD
Try Newey and Eyre or else CEF. You might find that your local branch doesn't carry them as stock, but they'll be able to get one from 'another' branch - perhaps for a small delivery fee.
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