I have Bosch proj. hdlts. on my 93 164s. Any idea if the low beam has a bulb that can be replaced or do I need to replace the entire unit? Only the low beam is out of commission. A sticker on the unit reads Bosch 301 086 201 HCR04 1814. Any suggestions on where I can get the bulb/unit? I have been unsuccessful with a google search.