As long as you know the centre bore of the alloy you want to buy then it would very likely be possible to get PCD converter spacers 'off the shelf'. Probably ebay.de would be your best bet for these, but some of the better UK wheel specialists may be able to advise you on availability. Another thing to watch would be that the converter spacers would have to bolt to the hub so would probably be a minimum of 15 - 20 mm thus you would need to make sure the wheels you are buying aren't any more than about 50mm offset, preverably a lot higher ET than that unless you know someone trustworthy to machine down the back of the alloys?