Not sure if these are available elsewhere but you can buy the following on eBay to sort out your trim clips:
Sliders: http://www.ebay.co.uk/itm/1307118414...ht_1323wt_1118
Clips: http://www.ebay.co.uk/itm/1608076152...ht_1546wt_1118
Disclaimer; haven't actually tried fitting these but they look spot on!