I figured, I kinda want my dashboard to be in good condition for a long long time, so I need something to block the sun from baking it everyday. Dash cover sounds like a good idea. The Mazda one costs $40... just a little bit expensive for what is essentially a big piece of foil. Then one day on my normal household shopping runs, they had the generic ones for $7.
Now the problem with the generic one is that it does not have very good fitting. For starters it's a rectangle.. and most windshields are not rectangles. It ended up being too wide and not long enough.
Ghetto solution time--using scissors and duct tape. So I grabbed the nearest tape measure, just to find out it wasn't long enough... so I just guesstimated on the dimensions.
I put it into the car to test fit, marked a few points, then cut cut cut! Which quickly solved my too wide issue. Now about that not long enough issues.... I did just cut off a bunch of extra foil. I taped it to the bottom. Turns out the area of the generic cover is pretty similar to the area of my windshield.
Final product.. fits decently well. Important part is it covers all of the dash.