Odd that getting an adaptor for a Gaslight proved such a struggle, as it is only a 27 mm clip-on which is used by Calor with their Patio gas cylinders, a commonly available product.
Probably in hind sight garden centres the more typical outlet for Calor's Patio gas, would have been a better source than those camping outlets you tried.
For info, the 27 mm clip-on is also used by the French Le Cube, but for them you need the vertical outlet version, whereas the Gaslights and Patio gas can also use the horizontal outlet as well as the vertical outlet type.
"27 mm Clip-on "vertical outlet " I could have got a regulator from a diy store but not an adaptor. Don’t you love Bulkhead regulators 😀