You can get both suction devices so you can stick them to the windscreen, and kneeboard-like devices so you can strap them to your leg.
Or do as I do - let the passenger hold them. It gives them something to look at and something to do during the flight.
As far as the IMC is concerned, you will learn to fly on whatever *certified* instruments there are in the plane.
AFAIK, a portable device can never be certified and thus cannot officially be used for navigation under IFR. (That they can augment your navigation and enhance your situational awareness is just a bonus.)