1. If you call Rivendell wanting to buy a headbadge, first thing they'll do is determine whether they have them. If they have them, then they'll ask to be convinced that you actually have the bike you claim to have. If they know you and know what bike you bought from them, no problem. If they have the headbadge and they are convinced that you are entitled to have one, then they will sell one to you. If they don't have them, or you are not entitled to have one, then you are out of luck.
2. Yes, in theory, but not in practice. If you lost yours, and all you have is photographs from flickr, and want to pay somebody to make something, you'll probably be looking at thousands of dollars, and lousy results. If you had the original in your hand and wanted a copy of that, then there are ways to get a copy made that would bring it down to the hundreds of dollars kind of range. A 3D scan and a metallic 3D print job is the most flexible. Then you'd paint it yourself.
If you are afraid of losing your headbadge, you should probably buy a replacement now. If you can't buy a replacement now, and are not motivated enough to spend a lot of money, then just try not to lose it, or resign yourself to the fact that if you lose it, it will be gone forever. Or post a WTB on here and offer to buy somebody's headbadge for $100. I bet there's somebody out there with your model of bike that would sell you their headbadge.
Bill Lindsay
El Cerrito, CA