The WoW Classic shop has opened its doors with a variety of items for your Wrath of the Lich King Classic and Cataclysm Classic collections*.
Here’s what’s currently in the shop inventory:

Auspicious Arborwyrm mount
Kalu’ak Whalebone Glider mount
Re-Awakened Phase-Hunter mount
 Pebble the Penguin (Pebble’s Pebble) pet
Dark Portal Hearthstone Effect
Fishspeaker’s Lucky Lure toy
Path of Illidan toy

Visit the Battle.net Shop or the in-game shop to purchase.
*WoW Classic Shop items only available in WoW Classic progression realms.