Does Apple sell European connectors individually?
Are you talking about the connectors that plug into the power supply?  I would not bother with Apple-branded connectors. They are called "duckhead connectors" and other brands are widely available, individually and in sets, online both in the U.S. and in Europe, and much less expensive than the ones that say Apple. And to my knowledge, Apple only sells them together, all the worldwide varieties in one box. Plug adapters are also widely and cheaply available.