Thanks Peter. The eBay items certainly look similar but I need to find the parts to match and fit the existing original components already on the car. I feel I must hold out for the stanchions specific to the D J1 F1.
A fellow J1 owner has very kindly come to the rescue and I am pleased to say I now have an original near side support for a J1 windscreen.
Although I have another possibility it would be very useful if an original for the driver's side could also be found. The support below is on a D-type.