Try the 'Poundshops'
I purchased a 'Turkey Roasting Tray' ( for - guess what - just £1).
It is a 'disposable' lightweight tray comprising of 'heavyweight aluminium foil'.
I use a Stove that sits on top of the gas cylinder.
I rested a pot on the stove top and measure the required height.
Cut this out of the 'tray' slightly larger. (say 20mm)
Then took this and 'wrapped' it around the stove (leaving a more than 'pan-sized' air-gap) for about 75% of the circumference and again cut this off slightly oversized (say 20mm)
Fold the edges back about 5mm on all 4 sides, then fold them 5mm again on all 4 sides (to give extra rigidity)
The windbreak cost £1 plus 10 minutes time and weighs 13 grams & is free standing when 'curved' in position.
WARNING - (this applies to shop bought, or home made windshields) do not make your windbreak fit too closely, or for the full circumference of the stove/ cartridge / pan as the reflected heat can overheat the gas cartridge and cause 'a catastrophic explosion'.
To start with, check the temperature of the gas cartridge every couple of minutes (touch it with your finger) until you are happy it will not overheat.
The advantage is that the heat reflected onto the cartridge will actually help with Gas flow in very cold conditions. I'm sure we have all seen the 'frost' produced on gas cylinders in cold weather, as the gas flow the pressure drops and the cartridge can freeze-up.
Alternatively (and avoiding the overheating cartridge problem) buy a nice big pie (Bakewell Tart etc) eat the pie and make a windbreak that fits directly to the stove.
By reflecting heat 'back-up' to the base of the pot you actually get 'more for your money' with a quicker boil (and less gas)
Not my picture - lifted from Google :