D3S bulbs are super expensive, I'm about to sell my OEMs bulbs soon since I'm changing to another temp, but I know u need a new one asap :-/ and I'm not ready to pull mine out quite yet... Even tho it's just sitting in the garage, check out eBay for OEM bulbs
i see them going for cheap on ebay like someone mentioned above, but there is so much fake (eg. philips) or "brand new" stuff that is actually used i just stay away from that place...
what temp range are you going with? what is oem? the ones i bought are 6000k only because they were the only ones in stock.