Halifax Mid-upper turret?

I have been asked to help locate a Halifax mid-upper turret! This request originated from the Halifax Aircraft Association and I hope it does not mean that the urge to change NA 337 from an “A” to a “B” has surfaced again!

The idea of building another centre fuselage section with the mid-upper and the H2S dome as a ‘side’ display was suggested some time ago to show the difference between the A and the B models.

Anyway does anyone know of any potential sources of, I assume, Boulton Paul Mk VIII turrets? I guess IWM must have one in their Stafford storage area but they will likely not want to give it up!

Thanks for any help you can give.