You will not get them from a UK source except main dealer on special order. They are available here in France no problem so you should be able to get them OK. If you are still in the UK then try going across the ditch and visiting a french depanvite, scrap yard. Or failing that main dealer.
You may also be able to get the clear non fluted H/lamp. They are not handed and its possible to reorient the dip.