It is true, that one panda is lonely. To get a companion panda in addition to your reward, follow these steps:
Click the Manage My Pledge button
Add the amount (from the reward listings) for the other panda you want
Send me a message via the contact creator link NOT in the comments
I will add your panda request to your backer report page.
I'll be checking as I review each day's pledges and will contact anyone who pledged enough for multiple pandas and check in with you if I haven't heard from you.