do you mean the bulb or the outside 'lens'? i bought some of the '8500k' bulbs listed on ebay for 9.99 a pair (see item 7980119506) and i am very happy with them so far. just a touch of blue, but brighter than standard.
What, exactly are siverstars? I changed a bulb with a sylvania something or other and it isn't quite as bright as the other lamp.
When changing the bulb, don't unscrew that phillips back there! That can ruin your evening.