As Jim pointed out you can order replacements from any MB dealer. If you know the folks at a dealership you can just call it in, otherwise they (understandably) need proof of ownership and location. I know the folks at my dealership and ordered some keys over the phone. It took about a week for them to show up. You can shorten that a lot by using priority overnight shipping. You might even call 1-800-222-0100 (MB client assistance center) and explain it to them. They are very accommodating folks!
'00 ML320 "Casper"
'92 400E "Stella"