Thanks Wagonqueen, if it comes to it, I'll just have to home brew a vacuum form jig to shape a new one (a group of us were already plotting to home build a vacuum form machine for a side business of making cosplay props).
In other news, it appears my escape hatch is fortunately a 26x26 standard unit, but given its age, I'll likely need to replace the whole thing.
I've already come to the conclusion that I'm going to have to steal the power vents off the KIT, the Fantastic Fans and Shurflo Comfort Breeze units have tripled in price since I last bought one.
