Hi,
I've got an almost-full box of Manthorpe Refurbishment Eaves Vents to spare. These are to add loft insulation (rock/sheep wool) closer to the edges in roofs ("fitted from inside the roof space to create a clear air gap between the loft insulation and felt, its flexible hinge enables it to achieve any roof pitch").
They're for 600mm Rafter Centres, but can be cut very easily to fit smaller widths.
The box has about 35 units free to a good home, all of them or just what you might need. Collect only, in CB1 Cambridge.