Well...Tech Support says the foam pieces are Not Available. Not sure how they could be anything BUT available inasmuch as they still sell that shroud and the current install instructions include the foam.
Anyhow, we took a 10-day trip using the A/C with a "roof" I made from sheet plastic. The system ran without incident in the same heat/humidity that had been shutting it down before.
I've since made my own foam pieces from a swim noodle as shown here:
In this pic, they're attached the top corners of the condenser frame with sheet metal screws and fender washers. The tore off when I tried to install the shroud. What I ended up doing, was tuck the two noodle pieces horizontally under the bottom edge of the shroud. Then I placed the shroud (Tuffmaxx, I don't know if a Coleman shroud will let you do that!) in place rear/condenser end first. I then worked the pieces up to vertical and rolled them to vertical at the edges of the coil. Rolling should be done so the rolling surface is the one against the coil face, and the dragging action is against the shroud.
Time'll tell, next trip...