they come in her shoes and socks as well as her accessories- which is probably why they aren't available for replacement, yet. If you don't have her shoes/socks, that would be one way to get them without getting all the accessories again. (Although they did change them, so if you have the old ones... you could get the new cap/necklace too. The shoes/socks would be cheaper)

I think the original idea of shoes and socks (and ribbons) was to act as the replacement part.