Blacking out rear windows?

I've got a tailgate with the window in that i wish to black out. I don't want to have the effort of removing it , or buying a new tailgate.

I was looking at the dark tinting kits , but from what I've seen the sun gets to them and they start to bubble and look pants after a while.

My current thought is to buy a big sheet of black or yellow vinyl, stick it on the outside and Stanley around the edge of the glass.

Anyone done this , or can recommended something else?