Finally got around to fixing it and fitting today, pics to share
The same late grill on the Pop top is also broken so it looks to me like a design flaw, the early grill has much thicker plastic here
measured up and cut some L shapes from Nylon with a hacksaw, doesn't need to be too accurate
Drilled through, the grill was drilled first and the L shape marked then drilled in a vice, then the final grill hole made, try to drill the whole thing in one go would break the grill I think.
add cable tie
fits great
Now to do the pop top