Regular hockey puck from Amazon or your local sport shop. Think its a 5/16" cap head bolt. 3/4 in length. (That is a 5/16" allen wrench), so it may be a larger diameter bolt (3/8") Either will work.
Put blue painter tape(or duct tape, any tape) on your drill bit to match depth of bolt. Find center/ drill hole. Use allen wrench to screw bolt
into the hockey puck. Good for 05/06 GT.
For the 17-22 GT same hockey puck, but use ceramic disc magnets( 1/2 inch Dia) stack of 4/5 and glue into hole. The NGT has an aluminum jack pad with a steel bolt. Magnets will hold hockey puck in place(centered) to the bolt.
Race ramps also work well in getting low clearance car high enough to use a floor jack. (or make your own from 2x12 lumber- one or two stacked and staggered)
I've been using a floor jack and jack stands for 19 years to work under the GT. Yes, Pete, a 4 post or two post lift would be nice.
The wheel cribs you posted will work for getting the car up to get the floor trays off and doing maintenance, unless you need to do suspension, steering or brakes.. Floor jacks work for almost everything. Lifts are even nicer.