It seems to me that Programmers is precisely that place.
Your complaint is that that particular site is not frequented by many of the recognized experts who regularly contribute to Stack Overflow. That's perfectly valid, of course; it's an easily verifiable fact.
But what strikes me as interesting is your next comment:
(and who can blame them?)
You seem to be implying that there are numerous problems with the Programmers site that make it sensible for these expert users not to frequent it, and since it's otherwise identical to Stack Overflow, those problems must be content-related.
And that brings us full-circle: You're requesting a place to ask questions that you yourself deem to sufficiently explain why expert programmers wouldn't be terribly interested in spending time on a site that contains them. That seems like a pretty good reason why such questions don't belong on SO, and it's hard to imagine why whichever site we decided they did belong on wouldn't already be (or at least, very quickly become) plagued by the exact same problems that you think afflict Programmers.
The questions asked and topics discussed on Programmers are of an undeniably different nature than those asked on Stack Overflow. If those questions are "uninteresting" to expert programmers, thus explaining why they're not equally regular contributors to the other site that hosts them, then why should we allow those questions to be asked on Stack Overflow? It seems that they would just clutter up the site with content that expert users don't really want to see and have no interest in contributing to.
About the only thing you can do is leave a comment for the particular users whom you'd like to see answer your question, directing them to the question posted on Programmers, and asking them to contribute their opinions. There's no guarantee that they'll do this, of course, but it's always an option.
Edit: In response to the second part of your question, questions that have been migrated to another site are clearly labeled as having been migrated from the original site, including a link back to the question as it was asked on that original site. It's a big banner with an arrow, just like shows up on a closed question. It's very unlikely that anyone will think the question was asked there in the first place.