Several years ago, I came across a post either here or on Beechtalk about someone making their own window shades using heat shield material from Home Depot. I did the same and I think I ended up having to buy two rolls to have enough material to make shades for all the windows. You simply place a section of the material large enough to cover the entire window and use a Sharpie to outline the shape by feel. I think the two rolls ended up costing me less than $25.
I have a Bruce's cover that came with my plane but I prefer my CB home made window shades. They weigh A LOT less, cost a fraction of a custom cover, take up less room in the plane, install from the inside in about 1 minute, keep prying eyes out and I don't risk the custom cover grinding sand onto the windows on a windy day. I wish I had a photo of them installed to show you but I can say they work great and have lasted 4 or 5 years now, still in good condition. I definitely wouldn't spend several hundred dollars like some of those pre made ones.
People will talk about the sun reflecting back through the glass and eventually causing crazing on the plexiglass. Yeah, maybe/probably if you keep your plane outside all the time, but for occasional use for a few days at a time, I don't see the harm. My plane normally lives in a hangar so they really only get used for several days per year.
https://www.homedepot.com/p/Everbilt-24-in-x-10-ft-Double-Reflective-Insulation-Radiant-Barrier-24x10DRI/314983628