Auster made quite a range of screens! Mine are about the same size as the modern Brooklands ones.
The windscreen on the black car may well be the same basic frame as on Melvyn's car, but the owner has definitely fitted non standard taller glass and may have extended the centre glass supports.
There are a number of people who make the frames for 2 and 3 speeders, but those frames would not fit the 5 speeder as it's a far wider car. I rather doubt any of them would want to make a screen as a one off, a lot of work, and the price would be huge.
In the UK such a screen would need to have windscreen wipers and washers. The fact you don't have them with aero-screens is based on being able to see ones road forward without glass or plastic in the way.
