where can I get windbg for windows 7 64bit without the whole sdk?

As was mentioned in the Stack Overflow answer you referenced in your question, you can download the tools from this page.

Once you've downloaded and run sdksetup.exe, waited for the suitcase screen to pass, you just need to click "Next" a couple of times. You'll get to this screen:

From there you can deselect everything except "Debugging Tools for Windows"