Itty bitty kid helmets

[Lapchik]

So my two year old son has started going on little sidecar rides around the block with me. I don't think we've cracked 15 miles an hour, so I've just been having him sit in the sidecar, without a helmet. I know, I know, insert hate comments below. Anyway, I want to get him a helmet. A bicycle helmet doesn't really do the job, and I want a full-face motorcycle helmet. I'm having a lot of trouble finding a real motorcycle helmet in a very very very small size. Does anyone know of a special size for small children? Or a manufacturer that has a line of kid's helmets?