Typically speaking Redline doesn't sell any products to the public. They import and distribute carbs, parts and kits to the vendors who retail them.
Now if you are in need of help solving a technical issue and then it is found that a part is necessary to remedy the issue they may opt to accommodate your need or more probable recommend you to a parts source.
Here is a number that should reach a trained tech @ Redline; 800 733 2277 ext. 7345
I provided you a link to one vendor in your previous thread. Navigating that site to all the various parts is a cinch, if you feel that you need the adapter plates it is part # 99004.551 or the gasket pack alone is # 99005.551
Trust me when I say that one adapter plate package is most likely not to be found to be any better than another. All of them need a close inspection and most likely a good sanding in order to eliminate any of the casting imperfections (high spots) that may cause an air leak.