The kit is out of production and Panda has shutdown operations. You will likely not be able to find this kit at any of the larger online shops. You might be able to locate one at one of the ship-specific shops such as Pacific Front http://www.pacificfront.com/
Trident Hobbies http://www.tridenthobbies.com/store/merchant.mv
or White Ensign http://www.whiteensignmodels.com/
If you try to contact Bill Gruner at Pacific Front -- call him after 11am Pacific Time. Bill is notorious for not answering emails, but he is a good guy to talk to, knowledgeable, and the service otherwise is very good. Chris Decker at Trident is also good to deal with, but he too is sometimes slow to answer email. John & Caroline Snyder at White Ensign are fantasic people to deal with, responsive to emails, they ship quickly - UK to Texas in less than a week.
As a last resort - I think that I have seen one of the Panda Burkes at Wild Bill's Hobbys in Irving Texas. The specific ship kit name you want for the Flight IIa is the USS Winston Churchill. Perhaps they will ship it to you.