uh? the one that goes behind the seat on a convertible? covers the spare tire? or goes between the seat and bracing?
I'm picking the spare tire.
if so here are some pictures of a "sort of " decent one
looks like 30" wide 3 inch hole(13 inches down from top of arc)for cover hold down
for cover hold down, 5"x 1" handle opening by trunk lock@12" start point,25.5" tall (not counting the tire round part), top part curve starts 5" in on one side and 5.5 on the passenger side for the Arc of the tire(could be wear and water damage causing the .5 difference). and the arc goes up 3 3/8 but I'd go 3.5 to adjust for wear. hope this helps