As is usual with any new product launch, accessories soon become available and in this case some of them are already in stock. UK online retailer Expansys has let us know about a range of cases they have in stock and some they have for pre-order.
BELKIN Cases for pre-order are here. Costing from £16.99
XtremeMac cases are now in stock here. Costing from £18.99
Casemate again for pre-order are here. Costing from £39.99
Or you can wait for the new design of Smart Cover from Apple.