OK, here is what I did, and it worked fine for me. Somewhere I heard that if you find, download and install the following apk:
VoiceSearch_1.5.apk
This will install and work on the Nexus the way the old app did, as as separate app from the Google search bar. And it worked fine for me.
You can do a search for that exact apk and you should be able to find a place hosting it for download, I just use Chrome to Phone (or Fox to Phone) to right-click and send it straight to my phone, then I just click on it to install it.
Here is the screenshot of it sitting on one of my home screens (I took it off of my bottom bar because I needed that space for stuff I actually used more). At first it had the square icon, like the old one, but then when it updated, I got this nice new round icon:
Click to view quoted image