where can I get a spare Dzus Clip?

I have a Baxi 130 He and one of the Dzus quarter turn clips that hold on the Air Box Door Panel is broken and it rattles. On the net the spare is 241139 but the postage charges and vat take this 22 mm square retainer to about £10.00 to £12.00 pounds. I have spent ages surfing. Does anyone know where these clips can be purchased at a reasonable price