5dmk3 focus peaking without liveview?

[MeHoo]

Pretty sure of the answer, but I thought I'd check...

I am using an external USB focusing device that I had hoped would work with the focus peaking on the HDMI monitor that I have, and it does, but I forgot how terribly slow the photo mode is in liveview.

Is there ANY way to get an external monitor purely for focusing (preferably for focus peaking) while using this setup or something similar for photo mode?

I need the lightning fast bursts and autofocus of non-live view, but as I forgot the 5dmk3 is not mirrorless, this seems impossible.  Dumb mistake of mine.

So do I go mirrorless, find some sort of viewfinder ehancer, or scrap the idea altogether?  I can use hdmi out or usb if needed if either helps.

Thanks in advance, but the specificity of my search yielded no answers.