UPDATE!
The screws are NOT M3!
I got hold of an M3 nut and bolt and the screws that hold the "glass" to the light will not go into the M3 nut.
A bit of web searching and I have discovered the thread is 6-32 UNC 32 t.p.i. and 32mm (1 1/4 in) long.
What chance of finding that as an A2 Stainless cap head Allen drive screw?
Easy!
I've just ordered the minimum quantity, ......100. £18.00
I need 18....
So, anyone want some? I'll send packs of 20 for £5.00 including postage to the first 4 people who contact me!
Bloody hell £18! My local garden machinery is brilliant for odd nuts, bolts, and grease nipples. I just replaced the rear brake adjusters on mine which were supplied to me without nuts. I got four 1/4" unf nuts off them for 52p. A quick Google for Salisbury reveals:
https://www.salisburygardenmachinery.co.uk/service-parts This looks pretty similar to the place I use in Worcester. Might be worth a call in future.