I used to sell window
mylar way back when at a home center - given it's what about 18 years ago now. Good idea, it is sort of see
thru from one side and reflective on both when hit by the light just right. 7777777777777777777777777777777777

(cat needs some attention.) Depending upon the tint it might be somewhat reflective on both sides when at least the interior side has a black
stage behind it. One side is certainly reflective, the other still made to see
thru as it's designed for a window.
Might look into car shops in addition to a stop by Home Depot to get the company that makes the stuff they sell.
Just checkeked Sweets Group catalog. LLumst Window Film is one brand of the stuff.
www.llumar.com Madico is another
www.madico.com.
MSC Specialty Films Inc.
www.solargard.com. 3M brand "Scotchtint" and Scotchshield - 3M should be a easy websearch. Given it's the 1999 version and some of these companies could be out of business. Section eight of the catalog if anyone has access to a more recent version. Sweets Group - you will find it in the architectural/building Materials section of a good library otherwise. Just a expensive encyclopedia like set of catalogs on stuff.