The quick answer is, yes many of us have Optical Viewfinders for our Q. For me, the single most useful Q Forum Thread has to be this one:
What Q accessories are worth it?
I find that my Yashica rangefinder OVF that came with 2 accessory lenses for the rangefinder (it's called a "Tele-Wide") works very well with my Q. It also helps conserve the battery, which is a big plus with the Q.
Here is my review of that particular OVF:
https://www.pentaxforums.com/accessoryreviews/yashica-tele-wide-viewfinder.html