I have a few 4:3 8ft across screens.
I gave 1 to a friend, and he took the screen out of the housing, and put it on a frame he built.
He is currently creating a motorized pulley system...similar to drafting table, that has the sliding straight edges. So depending on what format the show is in, the top and bottom will adjust pulling a velvet curtain.
My point is, with a pair of scissors, some wood, a nail gun, and maybe 1-2 hours, you could build a screen of any ratio.