Attaching lights - rubber bands

Got a nightlight during the week and while attempting to attach to my bars I succesfully (or unsuccessfully) snapped both "o" rings.(you get what you pay for I jury rigged it with some zip ties but anyone know where you can get the thick "o"ring type rubber bands or some other method of attaching to bars. So far have tried Sparts at Forestville, Clarks Rubber, Whitworths ( who had shock cord)........

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