How do I self close vote on my own question?

Question

My this question is no longer in the scope since the service has become obsolete. So, I just found that someone has already voted to close the question as off-topic with good reason:

I'm voting to close this question as off-topic because it can no longer be reproduced. The encrypted.google.com site no longer exists. – forest 20 mins ago

Now, I agree with the reason and want to vote for closing on that reason but I am not finding a way to do this. I'm not having close button yet and flag button doesn't include that feature I think. Also there is no button like "That's solved my problem" as we find in the case of closing as duplicate:

So-that community user can close the question automatically.

Now, how do I approach for self-closing my own question? Should I consider to use custom flag for mods?

Answer 1

Once you have 250 rep you will be able to do this. From the privileges page:

View Close Votes Privilege Type: Moderation Privilege

Awarded At: 250 Reputation

This privilege allows you to view and cast close and reopen votes on your own questions

Answer 2

As stated by Rory Alsop, users with 250 rep can vote to close your own question. Note that even if users self-vote their questions to be closed, it will be just another vote; it still won't be binding. (Only duplicate votes by gold badgers and all votes by mods are binding)

However, the alternative option is to delete your question as a courtesy for cleaning up, especially since it doesn't have any answers yet and obsolete/unanswerable at the same time.