You would need one 12.25 - 12.5" long for 12" wide film. Surface tension causes a bead at each edge that must be removed, so you need overwidth. You would have to coat a length of at least 22" - 24". However, I only have paper blades at this time. Film blades are a different design.

The cost would run in the range of $1300. These are 308 or 316 stainless, and are highly polished and built to 0.001" tolerance. It takes months to get one from the machine shop. Perhaps someone in the Steel City can do it for you!