I've been using the yoke so far (VFR flying), but I think
having the approach plates directly in your scan may be more
important.

Well, actually, my CFII insisted that after a proper approach briefing
you shouldn't really need to look at the plate much anymore. Certainly
not enough to warrant a need to have it in your scan. The minimum
altitudes should be memorized, as well as the first part of the missed.

I've thought about using the industrial strength suction
cup attached to the side window Lowrance includes (for cars).

Yep, the RAM mount suction cups will certainly work.

--
Thomas Borchert (EDDH)