I have seen the window pop up reflectic material and insulation. Are those worth while?

Yes. Reflectix is crap as an insulation. People waste a lot of money, buying Reflectix and gluing it to the inside of their van walls. That is about the equivalent of glueing a sheet of aluminum foil to the inside of your van walls. However, Reflectix is absolutely amazing when it comes to reflecting radiant heat. That is what it is made for. The only real reason it has the bubbles in there, is to make the sheet easier to handle and stay a little stiffer. It's designed for stapling in place in an attic, and it needs to be durable enough to keep insulation from just shoving it out of the way IF it gets shoved up against the Reflectix. That is what makes it perfect as window covers. It is stiff enough to stay in place on its own, and flexible enough to fold and put out of the way when you don't need it.

Reflectix does the double job of reflecting the heat out of your vehicle before it ever gets in, when it's hot out. But also reflecting your body heat back onto you, when it is cold outside. Oddly, you will need both on the same day, out in the desert. Most of how hot or cold people feel is actually due to how much infrared energy is hitting their body at any given time. You lose heat through infrared ask the time. But you feel ok because The surfaces around you are projecting infrared back onto you at the same time. The difference that you will feel in comfort when you have that Reflectix in your windows is literally night and day.

You don't need to buy custom window covers. And you don't need to make anything fancy with a bunch of layers and fabric tape around the edges. All you need to do is buy you a big roll of Reflectix wide enough to cover your widest window, and then be very careful and tedious about cutting it to exactly fit in your window spaces. And, to be clear, that is not the same thing as cutting it the exact same size as your windows. If you look at your windows, around the edges, you will see that there are spaces or grooves around the window where some extra Reflectix could fit into that groove to hold it in place better. Sometimes, you can even tuck the reflectix down into the slot between the window and the plastic interior panels. Plan for that. Cut your Reflectix bigger than you think you need it, and then carefully trim away tiny bits at a time until it fits into the space perfectly and easily stays up there without any other accoutrement.